U.S. patent application number 16/456571 was filed with the patent office on 2020-01-02 for aqueous polysulfide-based electrochemical cell.
The applicant listed for this patent is c/o FORM ENERGY INC.. Invention is credited to Yet-Ming Chiang, Lucas Cohen, Marco Ferrara, Mateo Cristian Jaramillo, Katelyn Ripley, Jessa Silver, Liang Su, Eric Weber, Theodore Alan Wiley, William Henry Woodford, Wei Xie.
Application Number | 20200006796 16/456571 |
Document ID | / |
Family ID | 68987619 |
Filed Date | 2020-01-02 |
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United States Patent
Application |
20200006796 |
Kind Code |
A1 |
Su; Liang ; et al. |
January 2, 2020 |
AQUEOUS POLYSULFIDE-BASED ELECTROCHEMICAL CELL
Abstract
An electrochemical cell and battery system including cells, each
cell including a catholyte, an anolyte, and a separator disposed
between the catholyte and anolyte and that is permeable to the at
least one ionic species (for example, a metal cation or the
hydroxide ion). The catholyte solution includes a ferricyanide,
permanganate, manganate, sulfur, and/or polysulfide compound, and
the anolyte includes a sulfide and/or polysulfide compound. These
electrochemical couples may be embodied in various physical
architectures, including static (non-flowing) architectures or in
flow battery (flowing) architectures.
Inventors: |
Su; Liang; (Medfield,
MA) ; Xie; Wei; (Waltham, MA) ; Chiang;
Yet-Ming; (Weston, MA) ; Woodford; William Henry;
(Cambridge, MA) ; Cohen; Lucas; (Newtown, PA)
; Silver; Jessa; (Roxbury, MA) ; Ripley;
Katelyn; (Queensbury, NY) ; Weber; Eric;
(Pittsburgh, PA) ; Ferrara; Marco; (Boston,
MA) ; Jaramillo; Mateo Cristian; (San Francisco,
CA) ; Wiley; Theodore Alan; (Somerville, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
c/o FORM ENERGY INC. |
Somerville |
MA |
US |
|
|
Family ID: |
68987619 |
Appl. No.: |
16/456571 |
Filed: |
June 28, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62692355 |
Jun 29, 2018 |
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62692414 |
Jun 29, 2018 |
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62716578 |
Aug 9, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/5815 20130101;
H01M 2300/0014 20130101; H01M 4/50 20130101; H01M 8/083 20130101;
H01M 8/184 20130101; H01M 8/1025 20130101; H01M 4/38 20130101; H01M
2/1626 20130101; H01M 2/1686 20130101; H01M 4/62 20130101; H01M
4/58 20130101; H01M 8/188 20130101; H01M 8/1266 20130101; H01M
10/281 20130101; H01M 10/0413 20130101; H01M 8/22 20130101 |
International
Class: |
H01M 8/18 20060101
H01M008/18; H01M 4/58 20060101 H01M004/58; H01M 4/50 20060101
H01M004/50; H01M 8/1246 20060101 H01M008/1246; H01M 2/16 20060101
H01M002/16; H01M 8/1025 20060101 H01M008/1025 |
Claims
1. An electrochemical cell comprising: a catholyte comprising a
cathode active material dissolved in an electrolyte; an anolyte
comprising a polysulfide compound dissolved in an electrolyte; and
an ion-permeable separator configured to electrically insulate the
anolyte from the catholyte.
2. The electrochemical cell of claim 1, wherein the cathode active
material comprises a manganese-based compound.
3. The electrochemical cell of claim 2, wherein the manganese-based
compound comprises a permanganate compound, a manganate compound,
or a combination thereof.
4. The electrochemical cell of claim 2, wherein the manganese-based
compound comprises potassium permanganate (KMnO.sub.4), potassium
manganate (K.sub.2MnO.sub.4), sodium permanganate (NaMnO.sub.4),
sodium manganate (Na.sub.2MnO.sub.4), lithium permanganate
(LiMnO.sub.4), lithium manganate (Li.sub.2MnO.sub.4), or any
combination thereof.
5. The electrochemical cell of claim 2, wherein the cathode active
material comprises a mixture of KMnO.sub.4 and NaMnO.sub.4.
6. The electrochemical cell of claim 2, wherein the catholyte
further comprises a compound configured to reduce
self-discharge.
7. The electrochemical cell of claim 6, wherein the compound is a
bismuth oxide, an alkaline earth metal salt, or an alkaline earth
metal hydroxide.
8. The electrochemical cell of claim 2, wherein the catholyte is
substantially nickel-free.
9. The electrochemical cell of claim 2, wherein the catholyte
further comprises an additive configured to sequester nickel.
10. The electrochemical cell of claim 2, wherein the separator
comprises: a polymer; and a protective layer disposed on a
catholyte side of the polymer and configured to reduce oxidation of
the polymer by the cathode active material.
11. The electrochemical cell of claim 10, wherein the protective
layer comprises manganese oxide.
12. The electrochemical cell of claim 10, wherein the protective
layer comprises a polyether ether ketone (PEEK), a polysulfone, a
polystyrene, a polypropylene, a polyethylene, or any combination
thereof.
13. The electrochemical cell of claim 1, wherein the separator
comprises an anion exchange membrane (AEM), a cation exchange
membrane (CEM), a zwitterionic membrane, a porous membrane with
average pore diameter smaller than 10 nanometers, a
polybenzimidazole-based membrane, a polysulfone-based membrane, a
polyetherketone-based membrane, a membrane including polymers of
intrinsic microporosity (PIM), or a combination thereof.
14. The electrochemical cell of claim 1, wherein: the cathode
active material comprises an iron-cyanide based compound; and the
electrochemical cell is a static cell.
15. The electrochemical cell of claim 14, wherein the iron-cyanide
based compound comprises a ferrocyanide compound, ferricyanide
compound, or a combination thereof.
16. The electrochemical cell of claim 14, wherein the iron-cyanide
based compound comprises: ferrocyanide anions
[Fe(CN).sub.6].sup.4-, ferricyanide anions [Fe(CN).sub.6].sup.3-,
or a combination thereof; and cations comprising Li.sup.+, K.sup.+,
Na.sup.+, or combinations thereof.
17. The electrochemical cell of claim 1, wherein at least one of
the catholyte and the anolyte comprises sodium thiosulfate
(Na.sub.2S.sub.2O.sub.3).
18. The electrochemical cell of claim 1, wherein the cathode active
material comprises a sulfur-based compound.
19. The electrochemical cell of claim 18, wherein the sulfur-based
compound comprises sulfur (S.sub.8), lithium (poly)sulfide
(Li.sub.2S.sub.x, where x=1 to 8), sodium (poly)sulfide
(Na.sub.2S.sub.x, where x=1 to 8), potassium (poly)sulfides
(K.sub.2S.sub.x, where x=1 to 8), or a combination thereof.
20. The electrochemical cell of claim 1, wherein the cathode active
material comprises a transition metal sulfide.
21. The electrochemical cell of claim 1, wherein: the cathode
active material comprises a manganese-based compound, iron-cyanide
based compound, or a sulfur-based compound; and the catholyte and
the anolyte are aqueous solutions having a pH at or above 10.
22. The electrochemical cell of claim 1, wherein: the cathode
active material comprises a manganese-based compound; and the
catholyte and the anolyte are aqueous solutions having a pH at or
above 13.
23. The electrochemical cell of claim 1, wherein the separator
comprises: an impermeable frame; and an ion-permeable membrane
disposed within the frame.
24. The electrochemical cell of claim 23, wherein: the membrane is
an anion exchange membrane that blocks cations and has a pore size
configured to block both cathode and anode active material anions
while permitting transition of hydroxide anions.
25. The electrochemical cell of claim 1, wherein the separator
comprises: an impermeable frame; and an ion-permeable membrane
disposed within the frame, wherein the ratio of the membrane area
to the sum of the membrane and frame areas is less than about
0.8.
26. The electrochemical cell of claim 1, further comprising: a
cathode immersed in the catholyte; and an anode immersed in the
anolyte.
27. The electrochemical cell of claim 2, wherein the separator
comprises a composite membrane comprising an inorganic material and
an organic material.
28. The electrochemical cell of claim 27, wherein the inorganic
material comprises a metal oxide or a ceramic material.
29. The electrochemical cell of claim 27, wherein the organic
material comprises a polyether ether ketone (PEEK), a polysulfone,
a polystyrene, a polypropylene, a polyethylene, or any combination
thereof.
30. The electrochemical cell of claim 2, wherein the positive
electrode comprises a carbon-based material and a metal oxide
coating layer configured to reduce oxidation of the carbon-based
material by the cathode active material.
31. The electrochemical cell of claim 1, wherein element sulfur is
added periodically to the anode active material to recover capacity
and rebalance the state of charge between anode and cathode.
32. The electrochemical cell of claim 2, wherein the cathode
comprises an oxygen reduction reaction (ORR) electrode that can be
operated to convert manganate to permanganate.
33. A power module, comprising: a stack of electrochemical cells,
the electrochemical cells each comprising: a catholyte comprising a
cathode active material dissolved in an electrolyte; an anolyte
comprising a polysulfide compound dissolved in an electrolyte; and
an ion-permeable separator configured to electrically insulate the
anolyte from the catholyte.
34. The power module of claim 33, wherein the cathode active
material comprises a manganese-based compound, iron-cyanide based
compound, or a sulfur-based compound.
35. The power module of claim 33, further comprising: a catholyte
tank fluidly connected to the electrochemical cells; and an anolyte
tank fluidly connected to the electrochemical cells, wherein the
catholyte flows between the catholyte tank and the electrochemical
cells and the anolyte flows between the anolyte tank and the
electrochemical cells, and wherein the cathode active material
comprises a manganese-based compound or a sulfur-based
compound.
36. The power module of claim 35, further comprising a pump
configured to increase an oxygen pressure applied to the catholyte,
wherein the cathode active material comprises a manganese-based
compound.
37. The power module of claim 35, further comprising a plurality of
catholyte tanks comprising the catholyte, wherein: the
electrochemical cells are arranged in columns and rows; the
electrochemical cells of each column are fluidly connected to a
respective one of the catholyte tanks; and the electrochemical
cells of each row are electrically connected to one other.
38. The power module of claim 35, wherein the separator comprises:
an impermeable frame; and an anion exchange membrane disposed
within the frame that blocks cations and has a pore size configured
to block cathode active material anions while permitting transition
of hydroxide anions.
39. The power module of claim 34, wherein the electrochemical cell
further comprises: a cathode immersed in the catholyte; and an
anode immersed in the anolyte.
40. The power module of claim 34, wherein the separator comprises
an anion exchange membrane (AEM), a cation exchange membrane (CEM),
a nanofiltration membrane, an ultrafiltration membrane, a reverse
osmosis membrane, a polybenzimidazole-based membrane, a membrane
including polymers of intrinsic microporosity (PIM), or a
combination thereof.
41. A bulk energy storage system, comprising: at least one battery
comprising a stack of electrochemical cells, each electrochemical
cell comprising: a catholyte comprising a cathode active material
dissolved in an electrolyte; an anolyte comprising a polysulfide
compound dissolved in an electrolyte; and an ion-permeable
separator configured to electrically insulate the anolyte from the
catholyte.
42. The bulk energy storage system of claim 41, wherein the cathode
active material comprises a manganese-based compound, iron-cyanide
based compound, or a sulfur-based compound.
43. The bulk energy storage system of claim 41, wherein the
separator comprises: an impermeable frame; and an anion exchange
membrane disposed within the frame that blocks cations and has a
pore size configured to block cathode active material anions while
permitting transition of hydroxide anions.
44. The bulk energy storage system of claim 42, wherein the
electrochemical cell further comprises: a cathode immersed in the
catholyte; and an anode immersed in the anolyte.
45. The bulk energy storage system of claim 42, wherein the
separator comprises an anion exchange membrane (AEM), a cation
exchange membrane (CEM), a nanofiltration membrane, an
ultrafiltration membrane, a reverse osmosis membrane, a
polybenzimidazole-based membrane, a membrane including polymers of
intrinsic microporosity (PIM), or a combination thereof.
46. The bulk energy storage system of claim 42, wherein the bulk
energy storage system is a long duration energy storage (LODES)
system.
47-77. (canceled)
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Provisional Patent Application No. 62/692,355 entitled "Aqueous
Sulfur-Polysulfide Electrochemical Cell" filed Jun. 29, 2018, U.S.
Provisional Patent Application No. 62/692,414 entitled
"Polysulfide-Ferrocyanide Electrochemical Cell" filed Jun. 29,
2018, and U.S. Provisional Application No. 62/716,578 entitled
"Aqueous Poly sulfide-Permanganate Electrochemical Cell" filed Aug.
9, 2018. The entire contents of all three applications are hereby
incorporated by reference for all purposes. This application is
related to U.S. Non-Provisional Patent Application Attorney Docket
No. 9284-012US entitled "Rolling Diaphragm Seal" filed on the same
date as this application and this application is related to U.S.
Non-Provisional Patent Application Attorney Docket No. 9284-019US
entitled "Metal Air Electrochemical Cell Architecture" filed on the
same date as this application. The entire contents of both related
applications are hereby incorporated by reference for all
purposes.
BACKGROUND
[0002] Energy storage technologies are playing an increasingly
important role in electric power grids; at a most basic level,
these energy storage assets provide smoothing to better match
generation and demand on a grid. The services performed by energy
storage devices are beneficial to electric power grids across
multiple time scales, from milliseconds to years. Today, energy
storage technologies exist that can support timescales from
milliseconds to hours, but there is a need for long and ultra-long
duration (collectively, at least >8 h) energy storage
systems.
[0003] This Background section is intended to introduce various
aspects of the art, which may be associated with embodiments of the
present inventions. Thus, the foregoing discussion in this section
provides a framework for better understanding the present
inventions, and is not to be viewed as an admission of prior
art.
SUMMARY
[0004] Embodiments of the present invention include apparatus,
systems, and methods for low-cost energy storage. In one example,
an electrochemical cell includes a catholyte, an anolyte, and a
separator disposed between the catholyte and anolyte and that is
permeable to the at least one ionic species (for example, a metal
cation or the hydroxide ion). The catholyte solution includes a
ferricyanide, permanganate, manganate, sulfur, and/or polysulfide
compound, and the anolyte includes a sulfide and/or polysulfide
compound. These electrochemical couples may be embodied in various
physical architectures, including static (non-flowing)
architectures or in flow battery (flowing) architectures.
[0005] According to various embodiments of the present disclosure,
provided is an electrochemical cell comprising: a catholyte
comprising a cathode active material dissolved in an electrolyte;
an anolyte comprising a polysulfide compound dissolved in an
electrolyte; and an ion-permeable separator configured to
electrically insulate the anolyte from the catholyte. In some
embodiments, the cathode active material may comprise a
manganese-based compound that may comprise a permanganate compound,
a manganate compound, or a combination thereof. In some
embodiments, the manganese-based compound comprises potassium
permanganate (KMnO.sub.4), potassium manganate (K.sub.2MnO.sub.4),
sodium permanganate (NaMnO.sub.4), sodium manganate
(Na.sub.2MnO.sub.4), lithium permanganate (LiMnO.sub.4), lithium
manganate (Li.sub.2MnO.sub.4), or any combination or mixture
thereof. In some embodiments, the cathode active material comprises
a mixture of KMnO.sub.4 and NaMnO.sub.4.
[0006] In some embodiments, the catholyte further comprises a
compound configured to reduce self-discharge. In some embodiments,
the compound is a bismuth oxide, an alkaline earth metal salt, or
an alkaline earth metal hydroxide. In some embodiments, the
catholyte is substantially nickel-free. In some embodiments, the
catholyte further comprises an additive configured to sequester
nickel. In some embodiments, the separator comprises a polymer and
a protective layer disposed on a catholyte side of the polymer and
configured to reduce oxidation of the polymer by the cathode active
material. In some embodiments, the protective layer comprises
manganese oxide. In some embodiments, the protective layer
comprises a polyether ether ketone (PEEK), a polysulfone, a
polystyrene, a polypropylene, a polyethylene, or any combination
thereof. In some embodiments, the separator comprises an anion
exchange membrane (AEM), a cation exchange membrane (CEM), a
zwitterionic membrane, a porous membrane with average pore diameter
smaller than 10 nanometers, a polybenzimidazole-based membrane, a
polysulfone-based membrane, a polyetherketone-based membrane, a
membrane including polymers of intrinsic microporosity (PIM), or a
combination thereof. In some embodiments, the cathode active
material comprises an iron-cyanide based compound, and the
electrochemical cell is a static cell. In some embodiments, the
iron-cyanide based compound comprises a ferrocyanide compound,
ferricyanide compound, or a combination thereof. In some
embodiments, the iron-cyanide based compound comprises:
ferrocyanide anions [Fe(CN).sub.6].sup.4-, ferricyanide anions
[Fe(CN).sub.6].sup.3-, or a combination thereof; and cations
comprising Li.sup.+, K.sup.+, Na.sup.+, or combinations thereof. In
some embodiments, at least one of the catholyte and the anolyte
comprises sodium thiosulfate (Na.sub.2S.sub.2O.sub.3). In some
embodiments, the cathode active material comprises a sulfur-based
compound. In some embodiments, the sulfur-based compound comprises
sulfur (S.sub.8), lithium (poly)sulfide (Li.sub.2S.sub.x, where x=1
to 8), sodium (poly)sulfide (Na.sub.2S.sub.x, where x=1 to 8),
potassium (poly)sulfides (K.sub.2S.sub.x, where x=1 to 8), or a
combination thereof. In some embodiments, the cathode active
material comprises a transition metal sulfide. In some embodiments,
the cathode active material comprises a manganese-based compound,
iron-cyanide based compound, or a sulfur-based compound, and the
catholyte and the anolyte are aqueous solutions having a pH at or
above 10. In some embodiments, the cathode active material
comprises a manganese-based compound, and the catholyte and the
anolyte are aqueous solutions having a pH at or above 13. In some
embodiments the concentration of the manganese-based compound is
>1M (mol/L concentration), such as 2M or 5M. In some embodiments
the concentration of the iron-cyanide based compound is >1M
(mol/L concentration), such as 2M or 5M. In some embodiments the
concentration of the sulfur-based compound is >1M (mol/L
concentration), such as 2M or 5M or 10M. In some embodiments, the
separator comprises an impermeable frame, and an ion-permeable
membrane disposed within the frame. In some embodiments, the
membrane is an anion exchange membrane that blocks cations and has
a pore size configured to block both cathode and anode active
material anions while permitting transition of hydroxide anions. In
some embodiments, the separator comprises an impermeable frame, and
an ion-permeable membrane disposed within the frame, wherein the
ratio of the membrane area to the sum of the membrane and frame
areas is less than about 0.8. In some embodiments, the
electrochemical cell further comprises a cathode immersed in the
catholyte, and an anode immersed in the anolyte. In some
embodiments, the separator comprises a composite membrane
comprising an inorganic material and an organic material. In some
embodiments, the inorganic material comprises a metal oxide or a
ceramic material. In some embodiments, the organic material
comprises a polyether ether ketone (PEEK), a polysulfone, a
polystyrene, a polypropylene, a polyethylene, or any combination
thereof. In some embodiments, the positive electrode comprises a
carbon-based material and a metal oxide coating layer configured to
reduce oxidation of the carbon-based material by the cathode active
material. In some embodiments, element sulfur is added periodically
to the anode active material to recover capacity and rebalance the
state of charge between anode and cathode. In some embodiments, an
auxiliary oxygen reduction reaction (ORR) electrode can be used as
a counter electrode to supply current that converts manganate to
permanganate.
[0007] According to various embodiments of the present disclosure,
provided is a power module comprising a stack of electrochemical
cells, the electrochemical cells each comprising: a catholyte
comprising a cathode active material dissolved in an electrolyte;
an anolyte comprising a polysulfide compound dissolved in an
electrolyte; and an ion-permeable separator configured to
electrically insulate the anolyte from the catholyte.
[0008] In some embodiments, the cathode active material comprises a
manganese-based compound, iron-cyanide based compound, or a
sulfur-based compound. In some embodiments, the power module
further comprises: a catholyte tank fluidly connected to the
electrochemical cells; and an anolyte tank fluidly connected to the
electrochemical cells, wherein the catholyte flows between the
catholyte tank and the electrochemical cells and the anolyte flows
between the anolyte tank and the electrochemical cells, and wherein
the cathode active material comprises a manganese-based compound or
a sulfur-based compound. In some embodiments, the power module
further comprises a pump configured to increase an oxygen pressure
applied to the catholyte, wherein the cathode active material
comprises a manganese-based compound. In some embodiments the tank
containing the catholyte is sealed such that no pump is needed to
apply additional oxygen pressure to the catholyte, as the
spontaneously generated oxygen accumulates and builds up oxygen
pressure to an equilibrium level of pressure. In some embodiments,
the power module further comprises a plurality of catholyte tanks
comprising the catholyte, wherein: the electrochemical cells are
arranged in columns and rows; the electrochemical cells of each
column are fluidly connected to a respective one of the catholyte
tanks; and the electrochemical cells of each row are electrically
connected to one other. In some embodiments, the separator
comprises: an impermeable frame; and an anion exchange membrane
disposed within the frame that blocks cations and has a pore size
configured to block cathode active material anions while permitting
transition of hydroxide anions. In some embodiments, the
electrochemical cell further comprises: a cathode immersed in the
catholyte; and an anode immersed in the anolyte. In some
embodiments, the separator comprises an anion exchange membrane
(AEM), a cation exchange membrane (CEM), a nanofiltration membrane,
an ultrafiltration membrane, a reverse osmosis membrane, a
polybenzimidazole-based membrane, a membrane including polymers of
intrinsic microporosity (PIM), or a combination thereof.
[0009] According to various embodiments of the present disclosure,
provided is a bulk energy storage system, comprising: at least one
battery comprising a stack of electrochemical cells, each
electrochemical cell comprising: a catholyte comprising a cathode
active material dissolved in an electrolyte; an anolyte comprising
a polysulfide compound dissolved in an electrolyte; and an
ion-permeable separator configured to electrically insulate the
anolyte from the catholyte. In some embodiments, the cathode active
material comprises a manganese-based compound, iron-cyanide based
compound, or a sulfur-based compound. In some embodiments, the
separator comprises: an impermeable frame; and an anion exchange
membrane disposed within the frame that blocks cations and has a
pore size configured to block cathode active material anions while
permitting transition of hydroxide anions. In some embodiments, the
electrochemical cell further comprises: a cathode immersed in the
catholyte; and an anode immersed in the anolyte. In some
embodiments, the separator comprises an anion exchange membrane
(AEM), a cation exchange membrane (CEM), a nanofiltration membrane,
an ultrafiltration membrane, a reverse osmosis membrane, a
polybenzimidazole-based membrane, a membrane including polymers of
intrinsic microporosity (PIM), or a combination thereof. In some
embodiments, the bulk energy storage system is a long duration
energy storage (LODES) system.
[0010] According to various embodiments of the present disclosure,
provided is an electrical system configured to manage the
variations in non-hydrocarbon based electricity generation to
provide predetermined uniform distribution of electricity, the
electrical system comprising: a) a means to generate electricity
from non-hydrocarbon energy sources; b) a long duration energy
storage system (LODES) comprising: i) a means for providing a
catholyte; ii) a means for providing an anolyte; iii) the means for
providing the anolyte, the means for providing the catholyte or
both comprising sulfur; and iv) a means for providing an ion
permeable separator disposed between the means for providing a
catholyte and the means for providing an anolyte; c) electrical
power transmission facilities; d) the means to generate electricity
from non-hydrocarbon energy sources, the LODES and the electrical
power transmission facilities, in electrical communication, whereby
electricity can be transmitted therebetween; and e) the electrical
system configured for electrical connection to a power grid, an
industrial customer, or both.
[0011] In some embodiments, the means for providing a catholyte
comprises a material selected from the group consisting of aqueous
polysulfide solution, Li.sub.2S.sub.x (where x is from 1 to 8),
Na.sub.2S.sub.x (where x is from 1 to 8), a saturated polysulfide,
and elemental sulfur. In some embodiments, the means for providing
an ion permeable separator comprises a material selected from the
group consisting of a dielectric material, a porous material, a
material permeable to hydroxide ions, a material permeable to
Li.sup.+, a material permeable to K.sup.+, a material permeable to
Na.sup.+, a material permeable to Cs.sup.+, a material permeable to
NH.sub.4.sup.+, and a material permeable to hydroxyl ions. In some
embodiments, the means for providing an ion permeable separator
comprises C.sub.7HF.sub.13O.sub.5S. C.sub.2F.sub.4, a sulfonated
tetrafluoroethylene, or a polyolefin. In some embodiments, the
means for providing an ion permeable separator is effectively
impermeable to active catholyte materials, active anolyte materials
or both. In some embodiments: the means for providing an ion
permeable separator is impermeable to active catholyte materials,
active anolyte materials or both; and the active catholyte or the
active anolyte materials are selected from the group consisting of
sulfur, polysulfides, sulfides, ferrocyanides and permanganates. In
some embodiments: the means for providing an ion permeable
separator is impermeable to active catholyte materials, active
anolyte materials or both; and the active catholyte or the active
anolyte materials are selected from the group consisting of sulfur,
polysulfides, sulfides, ferrocyanides and permanganates. In some
embodiments, the catholyte comprises an alkaline material. In some
embodiments, the catholyte comprises an electro positive material.
In some embodiments, the alkaline material comprises a material
selected from the group consisting of NaOH, LiOH, KOH, and
NH.sub.4OH. In some embodiments, the electro positive material
comprises an electropositive element selected from the group
consisting of Li.sup.+, K.sup.+, Na.sup.+, and NH.sub.4.sup.+. In
some embodiments, the anolyte comprises an alkaline material. In
some embodiments, the anolyte comprises an electro positive
material. In some embodiments, the alkaline material comprises a
material selected from the group consisting of NaOH, LiOH, KOH, and
NH.sub.4OH. In some embodiments, the electro positive material
comprises an electropositive element selected from the group
consisting of Li.sup.+, K.sup.+ and Na.sup.+, and NH.sub.4.sup.+.
In some embodiments, the means for providing an anolyte comprises
an anode active material selected from the group consisting of a
sulfide, a polysulfide a sulfide salt, a polysulfide salt, lithium
polysulfides (Li.sub.2S.sub.x, where x=1 to 8), sodium polysulfides
(Na.sub.2S.sub.x, where x=1 to 8) and potassium polysulfides
(K.sub.2S.sub.x, where x=1 to 8). In some embodiments, the means
for providing an anolyte comprises an anode active material
selected from the group consisting of a sulfide, a polysulfide a
sulfide salt, a polysulfide salt, lithium polysulfides
(Li.sub.2S.sub.x, where x=1 to 8), sodium polysulfides
(Na.sub.2S.sub.x, where x=1 to 8) and potassium polysulfides
(K.sub.2S.sub.x, where x=1 to 8). In some embodiments, the means
for providing a catholyte comprises a cathode active material. In
some embodiments, the catholyte defines a catholyte volume and the
anolyte defines an anolyte volume, and the catholyte volume is
about 1.5 to about 4 times larger than the anolyte volume. In some
embodiments, the catholyte defines a catholyte volume and the
anolyte defines an anolyte volume, and the catholyte volume is
about 1.5 to about 4 times larger than the anolyte volume. In some
embodiments, the catholyte defines a catholyte volume and the
anolyte defines an anolyte volume, and the catholyte volume is
about 1.5 to about 4 times larger than the anolyte volume. In some
embodiments, the means to generate electricity from non-hydrocarbon
energy sources is selected from the group consisting of a wind
farm, a thermal power plant, and a solar power plant. In some
embodiments, the LODES has a duration of about 24 hours to about
500 hours, and a power rating of from about 10 MW to about 50 MW.
In some embodiments, the LODES has a duration of about 8 hours to
about 2000 hours, and a power rating of from about 0.5 MW to about
500 MW. In some embodiments, the LODES has a duration of about 8
hours to about 100 hours, and a power rating of from about 0.5 MW
to about 500 MW. In some embodiments, the LODES has a duration of
about 24 hours to about 500 hours, and a power rating of from about
10 MW to about 50 MW. In some embodiments, wherein the LODES has a
round trip efficiency of at least about 70% to about 85%, at a
rated power density of at least about 11 mW/cm.sup.2. In some
embodiments, the LODES has a round trip efficiency of from about
50% to about 85%, at a rated power density of from about 9
mW/cm.sup.2 to about 30 mW/cm.sup.2. In some embodiments, the LODES
has a round trip efficiency of from about 65% to about 75%, at a
rated power density of from about 11 mW/cm.sup.2 to about 24
mW/cm.sup.2. In some embodiments, the system includes a hydrocarbon
based electrical power plant, an atomic energy based electric power
plant, or both.
[0012] According to various embodiments of the present disclosure,
provided is a method of operating an electrical system configured
to manage the variations in non-hydrocarbon based electricity
generation to provide predetermined uniform distribution of
electricity; the method comprising transferring electricity into a
long duration energy storage system (LODES), storing the
electricity in the LODES, transferring the electricity out of the
LODES; wherein the electrical system comprises: a) a means to
generate electricity from non-hydrocarbon energy sources; b) the
LODES comprising: i) a means for providing a catholyte; ii) a means
for providing an anolyte; iii) the means for providing the anolyte,
the means for providing the catholyte or both comprising sulfur;
and iv) a means for providing an ion permeable separator disposed
between the means for providing a catholyte and the means for
providing an anolyte; c) electrical power transmission facilities;
d) the means to generate electricity from non-hydrocarbon energy
sources, the LODES and the electrical power transmission
facilities, in electrical communication, whereby electricity can be
transmitted therebetween; and e) the electrical system configured
for electrical connection to a power grid, an industrial customer
or both.
DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is a schematic of an electrochemical cell, according
to various embodiments of the present disclosure with a static
(non-flowing) cell architecture.
[0014] FIG. 1B is a schematic of a power module according to
various embodiments based on the disclosed electrochemical cell of
FIG. 1A.
[0015] FIG. 2 is a schematic of an energy storage system, based on
the disclosed electrochemical cell, according to various
embodiments of the present disclosure with a flow battery (flowing)
architecture.
[0016] FIGS. 3A and 3B are schematic views of battery stacks that
may be used in an energy storage system, such as the system of FIG.
2, according to various embodiments of the present disclosure.
[0017] FIG. 4 is an experimental polarization curve obtained from
an exemplary flow cell.
[0018] FIG. 5 is experimental charge and discharge cycling data for
the exemplary flow cell tested in FIG. 4.
[0019] FIG. 6 is a chart showing the charge-related deposition of
sulfur species, according to various embodiments of the present
disclosure.
[0020] FIGS. 7A and 7B are schematic diagrams of a reduced active
area membrane separator, according to various embodiments of the
present disclosure.
[0021] FIG. 8 is a schematic view of cell including architecture
for reducing separator size, according to various embodiments of
the present disclosure.
[0022] FIG. 9 is a schematic view of flow battery connection
architecture configured to reduce shunt currents, according to
various embodiments of the present disclosure.
[0023] FIG. 10 is an isometric view of the overall structure of an
exemplary stack architecture.
[0024] FIG. 11A is an isometric view of one example stacked
configuration of multiple embodiment battery stacks.
[0025] FIG. 11B is an isometric view of another example stacked
configuration of multiple embodiment battery stacks.
[0026] FIGS. 12-20 illustrate various example systems in which one
or more aspects of the various embodiments may be used as part of
bulk energy storage systems.
DETAILED DESCRIPTION
[0027] The various embodiments will be described in detail with
reference to the accompanying drawings. Wherever possible, the same
reference numbers will be used throughout the drawings to refer to
the same or like parts. References made to particular examples and
implementations are for illustrative purposes and are not intended
to limit the scope of the claims. The following description of the
embodiments of the invention is not intended to limit the invention
to these embodiments but rather to enable a person skilled in the
art to make and use this invention. Unless otherwise noted, the
accompanying drawings are not drawn to scale.
[0028] As used herein, unless stated otherwise, room temperature is
25.degree. C. And, standard temperature and pressure is 25.degree.
C. and 1 atmosphere. Unless expressly stated otherwise all tests,
test results, physical properties, and values that are temperature
dependent, pressure dependent, or both, are provided at standard
ambient temperature and pressure.
[0029] Generally, the term "about" as used herein unless specified
otherwise is meant to encompass a variance or range of +10%, the
experimental or instrument error associated with obtaining the
stated value, and preferably the larger of these.
[0030] As used herein unless specified otherwise, the recitation of
ranges of values herein is merely intended to serve as a shorthand
method of referring individually to each separate value falling
within the range. Unless otherwise indicated herein, each
individual value within a range is incorporated into the
specification as if it were individually recited herein.
[0031] The following examples are provided to illustrate various
embodiments of the present systems and methods of the present
inventions. These examples are for illustrative purposes, may be
prophetic, and should not be viewed as limiting, and do not
otherwise limit the scope of the present inventions.
[0032] It is noted that there is no requirement to provide or
address the theory underlying the novel and groundbreaking
processes, materials, performance or other beneficial features and
properties that are the subject of, or associated with, embodiments
of the present inventions. Nevertheless, various theories are
provided in this specification to further advance the art in this
area. The theories put forth in this specification, and unless
expressly stated otherwise, in no way limit, restrict or narrow the
scope of protection to be afforded the claimed inventions. These
theories many not be required or practiced to utilize the present
inventions. It is further understood that the present inventions
may lead to new, and heretofore unknown theories to explain the
function-features of embodiments of the methods, articles,
materials, devices and system of the present inventions; and such
later developed theories shall not limit the scope of protection
afforded the present inventions.
[0033] The various embodiments of systems, equipment, techniques,
methods, activities and operations set forth in this specification
may be used for various other activities and in other fields in
addition to those set forth herein. Additionally, these
embodiments, for example, may be used with: other equipment or
activities that may be developed in the future; and, with existing
equipment or activities which may be modified, in-part, based on
the teachings of this specification. Further, the various
embodiments and examples set forth in this specification may be
used with each other, in whole or in part, and in different and
various combinations. Thus, for example, the configurations
provided in the various embodiments of this specification may be
used with each other; and the scope of protection afforded the
present inventions should not be limited to a particular
embodiment, configuration or arrangement that is set forth in a
particular embodiment, example, or in an embodiment in a particular
figure.
[0034] An electrochemical cell, such as a battery, stores
electrochemical energy by separating an ion source and an ion sink
at differing ion electrochemical potentials. A difference in
electrochemical potential produces a voltage difference between the
positive and negative electrodes; this voltage difference will
produce an electric current if the electrodes are connected by a
conductive element. In a battery, the negative electrode and
positive electrode are connected by external and internal
conductive elements in parallel. Generally, the external element
conducts electrons, and the internal element (electrolyte) conducts
ions. Because a charge imbalance cannot be sustained between the
negative electrode and positive electrode, these two flow streams
supply ions and electrons at the same rate. In operation, the
electronic current can be used to drive an external device. A
rechargeable battery can be recharged by application of an opposing
voltage difference that drives an electronic current and ionic
current in an opposite direction as that of a discharging battery
in service.
[0035] Embodiments of the present invention include apparatus,
systems, and methods for long-duration, and ultra-long-duration,
low-cost, energy storage. Herein, "long duration" and/or
"ultra-long duration" may refer to periods of energy storage of 8
hours or longer, such as periods of energy storage of 8 hours,
periods of energy storage ranging from 8 hours to 20 hours, periods
of energy storage of 20 hours, periods of energy storage ranging
from 20 hours to 24 hours, periods of energy storage of 24 hours,
periods of energy storage ranging from 24 hours to a week, periods
of energy storage ranging from a week to a year (e.g., such as from
several days to several weeks to several months), etc. In other
words, "long duration" and/or "ultra-long duration" energy storage
cells may refer to electrochemical cells that may be configured to
store energy over time spans of days, weeks, or seasons. For
example, the electrochemical cells may be configured to store
energy generated by solar cells during the summer months, when
sunshine is plentiful and solar power generation exceeds power grid
requirements, and discharge the stored energy during the winter
months, when sunshine may be insufficient to satisfy power grid
requirements.
[0036] According to various embodiments, an electrochemical cell
includes a catholyte, an anolyte, and a separator disposed between
the cathode and anode and that is permeable to the at least one
metal ion. According to various embodiments, an electrochemical
cell includes a catholyte, an anolyte, and a separator disposed
between the cathode and anode and that is permeable to the at least
one metal ion or the hydroxide ion. The catholyte may be an aqueous
solution containing one or more permanganate compounds dissolved in
a liquid. The catholyte may include sulfur and the anolyte may
include sulfide or polysulfide. The anolyte may be an aqueous
solution which contains one or more polysulfide compounds.
Optionally, there may be a cathode and/or an anode, which are solid
electrodes, upon which surfaces the positive and negative electrode
reactions are conducted. The cathode may be immersed in the
catholyte and the anode may be immersed in the anolyte.
[0037] In various embodiments, a polysulfide battery may include an
aqueous liquid catholyte contacting a cathode current collector in
a cathode chamber, an aqueous liquid anolyte contacting an anode
current collector in an anode chamber, and a separator separating
the catholyte in the cathode chamber from the anolyte in the anode
chamber. In various embodiments, the anolyte may include an aqueous
polysulfide solution (AqS), such as Li.sub.2S.sub.x and/or
Na.sub.2S.sub.x solution, in which x ranges from 1 to 8 (e.g.,
Li.sub.2S and/or Na.sub.2S when x=1). In various embodiments, the
battery may be a flow battery (i.e., flowing battery, which is also
sometimes called a regenerative fuel cell) containing a pump which
circulates the catholyte and/or the anolyte, or a non-flowing
battery which lacks the circulation pump, or a semi-flow battery in
which only one of the anolyte or catholyte is circulated while the
other is static.
[0038] In some embodiments, both the anolyte (or anode) and the
catholyte (or cathode) may maintain a solid-liquid equilibrium and
may be configured to maintain saturated polysulfide species in a
liquid. That is, at very low electrochemical cycling rates, liquid
saturation may be maintained by dissolving the solid. In various
embodiments where the battery may include S.sub.8--Li.sub.2S.sub.8
as the catholyte and Li.sub.2S--Li.sub.2S.sub.4 as the anolyte, the
battery may have an open current voltage (OCV) of about 0.45V or
higher, depending on the concentration of sulfur. In addition, such
an embodiment battery may have a high energy density because energy
storage may occur in precipitated sulfur species and is therefore
not limited by the solubility of sulfur or sulfide in the liquid
electrolyte.
[0039] FIG. 1A is a schematic view of an aqueous polysulfide-based
electrochemical cell 100, according to various embodiments of the
present disclosure in which the anolyte and catholyte are static
(non-flowing). Referring to FIG. 1A, the cell 100 includes a
housing 110 in which are disposed a positive electrode 112 or
cathode, a negative electrode 114 or anode, a separator 116
disposed between the cathode 112 and the anode 114, a catholyte
122, and an anolyte 124.
[0040] The housing 110 may be formed of a polymer, such as
high-density polyethylene, polypropylene, or the like. The housing
110 may include a first chamber in which the catholyte 122 is
disposed, and a second chamber in which the anolyte 124 is
disposed. In some embodiments, the housing 110 may be configured to
contain from about 600 liters (L) to about 1200 L of the catholyte
122, such as about 900 L, and from about 1000 L to about 1500 L of
the anolyte 124, such as about 1250 L. In other words, the cell 100
may include a first volume of the catholyte 122 and a second volume
of the anolyte 124, with the second volume ranging from about one
times to about two times, such as about 1.3 times to about 1.7
times, the first volume. In some embodiments, the housing 110 may
be configured to contain from about 3500 L to about 4000 L of the
catholyte 122, such as about 3750 L, and from about 1000 L to about
1500 L of the anolyte 124, such as about 1250 L. In other words,
the cell 100 may include a first volume of the catholyte 122 and a
second volume of the anolyte 124, with the first volume ranging
from about 2 times to about four times, such as about three times,
the second volume.
[0041] The cell 100 may include one or more gaskets 130 configured
to seal the cathode 112, anode 114, separator 116, catholyte 122,
and anolyte 124 in the housing 110. For example, the gaskets 130
may be formed of a rubber material, such as ethylene propylene
diene monomer (EPDM) or the like. As the cathode 112, anode 114,
separator 116, catholyte 122, and anolyte 124 may be sealed in the
housing 110, the cell 100 may be a static cell.
[0042] The separator 116 may be formed of a dielectric material, or
a porous material, that is permeable to positive ions, such as Li,
K.sup.+, Na.sup.+, Cs.sup.+, and/or NH.sub.4.sup.+ ions, or
negative ions, such as hydroxide ions. The separator 116 may be
impermeable or effectively impermeable to active materials of the
catholyte and anolyte 122, 124, such as sulfur, polysulfides,
ferrocyanides, and/or permanganates. Herein "effectively
impermeable" refers to a separator that prevents crossover of at
least 90%, such as at least 95%, at least 97%, at least 98%, or at
least 99% of active materials for a time period ranging from about
1 month to about 1 year. In some embodiments, the separator 116 may
be permeable to anions such as hydroxyl (OH.sup.-) ions. In some
embodiments, the separator 116 may be a membrane, such as a
membrane formed from a polymer with a tertrafluoroethylene backbone
and side chains of perfluorovinyl ether groups terminated with
sulfonate groups (e.g., a sulfonated tetrafluoroethylene membrane,
a membrane made of C.sub.7HF.sub.13O.sub.5S. C.sub.2F.sub.4, a
membrane made of polymers sold under the Nafion brand name, etc.)
or the like. For example, the separator 116 may comprise a porous
polyolefin film, a glass fiber mat, a cotton fabric, a rayon
fabric, cellulose acetate, paper, or the like.
[0043] A cathode current collector 118 may be electrically
connected to the cathode 112, and an anode current collector 120
may be electrically connected to the anode 114. The current
collectors 118, 120 may be formed of a conductive material, such as
stainless steel, carbon, titanium, combinations thereof, or the
like. The thickness of current collectors 118, 120 may range from
about 0.05 cm to about 0.5 cm, such as from about 0.1 cm to about
0.3 cm, or about 0.2 cm.
[0044] The cathode 112 may include a conductive layer having a high
surface area, such as a carbon felt layer or nickel foam layer, and
may be disposed between the cathode current collector 118 and the
separator 116. The cathode 112 may be configured to facilitate
electrochemical reactions with the active materials of the
catholyte 122. The cathode 112 may be non-flowing. In certain
embodiments the catholyte 122 may be quiescent. In certain other
embodiments, the catholyte 122 may be stirred to promote more rapid
mass-transport.
[0045] The anode 114 may include a conductive high surface area
layer, such as a nickel foam or nickel felt layer, and may be
disposed between the anode current collector 120 and the separator
116. The anode 114 may be configured to facilitate electrochemical
reactions with the active materials of the anolyte 124. The anode
114 may be non-flowing. In certain embodiments the anolyte 124 may
be quiescent. In certain other embodiments, the anolyte 124 may be
stirred to promote more rapid mass-transport.
[0046] The catholyte and anolyte 122, 124 may include alkaline
slurries, suspensions, solutions, or mixtures of solids and
solutions. The catholyte and anolyte 122, 124 may both include an
electropositive element, such as Li.sup.+, K.sup.+, Na.sup.+, or
combinations thereof. For example, it has been found that including
multi-valent electropositive elements, such as a combination of
Li.sup.+, K.sup.+, and/or Na.sup.+, may increase cell potential and
decrease the crossover of redox ions, such as polysulfide,
permanganate, and/or ferrocyanide compounds. When the catholyte and
anolyte 122, 124 are fully soluble, the ionic conductivity is
maximized, allowing for the thickness of the anolyte and catholyte
chambers to be maximized. When the catholyte 122 and anolyte 124
are slurries, comprised of mixtures of solid and liquid phases, the
energy density per unit volume is increased, but at the cost of
diminished ion-phase transport.
[0047] An alkaline agent may be added to the catholyte and anolyte
122, 124 in an amount sufficient to provide a pH of at least 9,
such as a pH ranging from about 9 to about 14, such as a pH ranging
from about 13 to about 14. In some embodiments, the alkaline agent
may be, for example, a strong base such as NaOH, LiOH, KOH, or the
like. In some embodiments, the alkaline agent may be a mixture of
such strong bases, such as a mixture of NaOH and LiOH, or a mixture
of NaOH and KOH, or a mixture of NaOH, LiOH, and KOH. In some
embodiments, dissociation of the alkaline agent may provide the
electropositive element. In other embodiments, a salt comprising
the electropositive element may be added to the catholyte and
anolyte 122, 124.
[0048] The catholyte 122 may include a cathode active material
(e.g., a material configured to adsorb and desorb working ions such
as Li.sup.+, Na.sup.+, and K.sup.+) dissolved in an electrolyte,
such as aqueous electrolyte, and the anolyte 124 may include an
anode active material dissolved in an electrolyte, such as an
aqueous electrolyte.
[0049] For example, the anode active material may include a sulfide
or polysulfide compound or salts thereof. For example, the anode
active material may include lithium polysulfides (Li.sub.2S.sub.x,
where x=1 to 8), sodium polysulfides (Na.sub.2S.sub.x, where x=2 to
8) and/or potassium polysulfides (K.sub.2S.sub.x), where x=1 to
8.
[0050] The anolyte 124 may have an anode active material
concentration ranging from about 4M to about 14M, such as from
about 5M to about 12M, or from about 7M to about 10M. At an anolyte
active material concentration of 2.5M (S.sub.2.sup.2-), the anolyte
capacity density may be about 67.0 Ah/L. However, the present
disclosure is not limited to any particular concentration of anode
active material.
[0051] The catholyte 122 may have a cathode active material
concentration ranging from about 0.5 mol/L (M) to about 14M.
However, the cathode active material concentration may vary
depending on the particular active material utilized and/or
particular electrochemical cell and/or system applications.
Accordingly, the present disclosure is not limited to any
particular active material concentration.
[0052] FIG. 1B is a schematic view of a power module 390 according
to various embodiments including multiple cells 100 connected
together to form stacks 392. With reference to FIGS. 1A and 1B, the
power module may include one or more stacks 392. In some
embodiments, a stack 392 may include one cell 100. In some
embodiments, a plurality of electrochemical cells 100 may be
connected in series to form a stack 392. In some embodiments, the
stack 392 may include or may include cells 100, such as two (2) to
one hundred (100) cells 100, or for example, fifty (50) cells 100,
twenty-two (22) cells 100, etc. In various embodiments, the stack
300 may be comprised of four (4) to twenty (20) cells 100, such as
six (6) cells 100. For example, the stacks 392 illustrated in FIG.
1B are shown including three (3) cells 100. While illustrated as
including three (3) cells 100, the stacks 392 may include more or
less cells 100. In some embodiments, a stack 392 may have a round
trip efficiency (i.e., the amount of energy that a storage system
can deliver relative to the amount of energy injected into the
system during the immediately preceding charge) of at least 75% at
a rated power density of about 24 mW/cm.sup.2. In some embodiments,
a stack 392 may have a 12 mW/cm.sup.2 power density and an area
specific resistance (ASR) of about 4.2 .OMEGA.-cm.sup.2, or less.
Such a stack 392 may have a self-discharge rate of about 0.5% per
week, or less.
[0053] In some embodiments, a plurality of stacks 392, such as two
or more stacks 392, may be electrically connected together in
parallel to form a power module 390. For example, FIG. 1B
illustrates three (3) stacks 392 connected in parallel to form a
power module 390. While illustrated as including three (3) stacks
392, the power module 390 may include more or less stacks 392. As
one example, thirty-two (32) of stacks 392 may be electrically
connected in parallel to form a power module 390, which may have a
rated power of 7.6 kW. The nominal module voltage and current of
such a thirty-two (32) stack 392 module 390 may be 10V and 800 A,
respectively, which may enable using low-cost power electronics for
the stack 392 electrical system.
[0054] In various embodiments, the power module 390 and/or stack(s)
392 may be connected to additional balance of plant elements, such
as an inverter, heat exchanger, etc. However, hydraulic elements,
such as system pumps and auxiliary reservoirs found in conventional
flow battery systems may be omitted in the power module 390 and/or
stack(s) 392 according to various embodiments of the present
disclosure in which the anolyte and catholyte are static
(non-flowing).
[0055] FIG. 2 is a schematic view of an aqueous polysulfide-based
electrochemical cell system 200, according to various embodiments
of the present disclosure, in which the system uses a flowing
anolyte 124 and catholyte 122. Referring to FIG. 2, the system 200
includes an anolyte tank 201 in which the anolyte 124 is disposed
and a catholyte tank 202 in which the catholyte 122 is disposed.
The catholyte 122 and anolyte 124 may include anode and cathode
active materials as discussed above with regard to FIG. 1A.
[0056] The system further comprises anolyte tubing 211 and
catholyte tubing 212, through which the anolyte and catholyte,
respectively, are induced to flow, by anolyte pump 221 and
catholyte pump 222. The system 200 includes electrochemical cell
stacks 300 into which the anolyte 124 and catholyte 122 are pumped,
to allow the electrochemical reactions to occur. The system 200 may
include any suitable number of stacks 300, which may be
electrically connected in parallel or series, for example. The
connected stacks 300 may form a power module 391.
[0057] FIG. 3A is a schematic view of an electrochemical cell stack
300, according to various embodiments of the present disclosure. In
some embodiments, the stack 300 may be configured as a flow type
cell uses a flowing anolyte 124 and catholyte 122. For example FIG.
2 illustrates the stack 300 in use in flow type system 200.
However, the stack 300 is not limited to flow type uses, and in
other embodiments, the stack 300 may be static type cell in which
the anolyte 124 and catholyte 122 do not flow. Referring to FIGS. 2
and 3A, the stack 300 includes a housing (or frame) 304 in which
one or more unit cells 302 are disposed. For example, the stack 300
may include only one unit cell 302 in some embodiments. In other
embodiments, the stack 300 may include multiple unit cells 302,
such as two (2) to one hundred (100) unit cells 302, or for
example, fifty (50) unit cells 302, twenty-two (22) unit cells 302,
etc. In various embodiments, the stack 300 may be comprised of four
(4) to twenty (20) unit cells 302, such as six (6) unit cells 302.
A plurality of such stacks 300 may be electrically connected in
parallel to form a power module (e.g., the power module 391 in a
flow configuration or a different power module in a static
configuration). The power module and/or stack(s) 300 may be
connected to additional balance of plant elements, such as an
inverter, heat exchanger, etc. However, hydraulic elements, such as
system pumps and auxiliary reservoirs found in conventional flow
battery systems may be omitted when the power module and/or a
stack(s) 300 are used in static battery systems.
[0058] Each unit cell 302 may include a positive electrode 312 or
cathode, a negative electrode 314 or anode, a separator 316
disposed between the cathode 312 and the anode 314, a cathode
current collector 318, and an anode current collector 320. In some
embodiments, the electrodes 312, 314 may include conductive high
surface area materials, such as a nickel foam or nickel mesh or a
carbon felt.
[0059] The stack 300 may include gaskets 308 configured to at least
partially seal each unit cell 302. For example, the gaskets 308 may
be formed of a rubber material, such as ethylene propylene diene
monomer (EPDM) or the like. The separator 316 may be formed of a
dielectric material permeable to positive ions. For example, the
separator 316 may comprise a porous polyolefin film, a glass fiber
mat, a cotton fabric, a rayon fabric, cellulose acetate, paper, or
the like.
[0060] The housing (or frame) 304 may be formed of a polymer, such
as high-density polyethylene (HDPE), polypropylene (PP), or the
like. In other embodiments, the housing (or frame) 304 may be
formed of a metallic material, such as steel, stainless steel,
aluminum, or the like. The housing (or frame) 304 may include
tension rods 306 configured to apply pressure to the cells 302 via
the housing (or frame) 304. In this manner, the tension rods 306
and housing (or frame) 304 together may act as a biasing device.
The tension rods 306 may be formed of an electrically conductive
material. In some embodiments, the current collectors 318, 320 may
be electrically connected to the tension rods 306, such that the
cells 302 are electrically connected in series.
[0061] In some embodiments, the cells 302 may be arranged in the
stack 300 in one or more cell repeat units. In a stack 300, the
number of unit cells 302 may be adjusted to tune variously the
absolute current, in Amperes, or voltage, in Volts, or power, in
Watts, of the system. In certain embodiments the unit cells 302 may
be connected electrically in parallel or in series, to add either
voltage or current. In certain embodiments the unit cells 302 may
be connected in a combination of parallel and series. In certain
embodiments the unit cells 302 may be connected hydraulically in
parallel or in series, or in mixed parallel/series
configurations.
[0062] The current collectors 318, 320 may be formed of a
conductive material, such as stainless steel, carbon, titanium,
combinations thereof, or the like. The thickness of the current
collector 318, 320 may range from about 0.05 cm to about 0.5 cm,
such as from about 0.1 cm to about 0.3 cm, or about 0.2 cm. In some
embodiments, the current collectors 318, 320 may be at least
partially porous.
[0063] During charging and discharging, various anode active
material species, such as sulfur species, may be reversibly formed
at the anodes 314, and various cathode active material species,
such as sulfur, polysulfides, ferrocyanide, permanganate, and/or
manganate species may be reversibly formed at the cathodes 312, in
order to store and discharge power.
[0064] FIG. 3B is a schematic view of an alternative
electrochemical cell stack 301 that may be used in place of one or
more of the stacks 300, according to various embodiments of the
present disclosure. In some embodiments, the stack 301 may be
configured as a flow type cell uses a flowing anolyte 124 and
catholyte 122. However, the stack 301 is not limited to flow type
uses, and in other embodiments, the stack 300 may be static type
cell in which the anolyte 124 and catholyte 122 do not flow. The
stack 301 is similar to the stack 300, so only the differences
therebetween will be discussed in detail.
[0065] Referring to FIG. 3B, the stack 301 includes cathodes 312
that are each disposed on opposing sides of cathode current
collectors 318, and anodes 314 disposed on opposing sides of anode
current collectors 320. In particular, the current collectors 318,
320 may be immersed in or coated on opposing sides respectively
with a cathode material and an anode material. Accordingly, the
amount of cathode and anode material in each cell 302 may be
increased, as compared to the cells 302 of the stack 300. Similar
to stack 300 described above, stack 301 may include may include
only one unit cell 302 in some embodiments. Similarly, in other
embodiments, the stack 301 may include or may include multiple unit
cells 302, such as two (2) to one hundred (100) unit cells 302, or
for example, fifty (50) unit cells 302, twenty-two (22) unit cells
302, etc. In various embodiments, the stack 301 may be comprised of
four (4) to twenty (20) unit cells 302, such as six (6) unit cells
302. In one example, the stack 301 may have twenty-two (22) unit
cells 302 connected in series. In such an example stack 301, may
have a round trip efficiency of at least 79% at a rated power
density of about 11 milliwatts per square centimeter (mW/cm.sup.2).
As another example, the stack 301 may have a 12 mW/cm.sup.2 power
density and an area specific resistance (ASR) of about 4.2
.OMEGA.-cm.sup.2, or less. Such an example stack 301 may have a
self-discharge rate of about 0.5% per week, or less. A plurality of
such stacks 301 may be electrically connected in parallel to form a
power module (e.g., the power module 391 in a flow configuration or
a different power module in a static configuration). For example,
when thirty-two (32) stacks 301 may be electrically connected in
parallel to form a power module, such an example power module may
have a rated power of 7.6 kW. The nominal module voltage and
current of such an example power module may be 10V and 800 A,
respectively, which may enable the use of low-cost power
electronics for the stack electrical system. The power module
and/or stack(s) 301 may be connected to additional balance of plant
elements, such as an inverter, heat exchanger, etc. However,
hydraulic elements, such as system pumps and auxiliary reservoirs
found in conventional flow battery systems may be omitted when the
power module and/or a stack(s) 301 are used in static battery
systems.
[0066] According to various embodiments (for example any of the
cells 100, 302 and/or stacks 392, 300, 301) of the present
disclosure, a separator or membrane may be used as the "physical
barrier" or "container" of either the catholyte or anolyte. The
membrane or separator may serve as all or part of the "wall of the
container". In various embodiments, the membrane or separator may
be a pliable form, such as a bag. Such a modular membrane-bag cell
may be placed in a pool of counter electrolyte during battery
operation in either floating or submerging fashion.
[0067] Manganese-Based Cathode Active Materials
[0068] In various embodiments (for example any of the cells 100,
302 and/or stacks 392, 300, 301), the cathode active material may
include one or more manganese-based compounds. Herein, a
"manganese-based compound" cathode active material is intended to
encompass compounds including permanganate anions MnO.sub.4.sup.-,
and compounds including manganate anions MnO.sub.4.sup.2-, and
salts thereof. These compounds may be referred to as aqueous
permanganate compounds (AqMn) when dissolved in an aqueous
electrolyte. In certain embodiments, the manganese-based compounds
may be in the form of salts associated with a working ion, such as
K.sup.+, Li.sup.+, or Na.sup.+. For example, such manganese-based
salts may include potassium permanganate (KMnO.sub.4), potassium
manganate (K.sub.2MnO.sub.4), sodium permanganate (NaMnO.sub.4),
sodium manganate (Na.sub.2MnO.sub.4), lithium permanganate
(LiMnO.sub.4), or lithium manganate (Li.sub.2MnO.sub.4). In certain
embodiments, the cathode active material may include a plurality of
different permanganate compounds, such as a mixture of KMnO.sub.4
and NaMnO.sub.4, which may be abbreviated as (K, Na)MnO.sub.4.
[0069] In some embodiments (for example any of the cells 100, 302
and/or stacks 392, 300, 301), a catholyte may have a permanganate
or manganate compound concentration ranging from about 0.5M to
about 10M, such as from about 1M to about 5M, or from about 2M to
about 4M. At a catholyte concentration of 3.5M of MnO.sub.4.sup.+
the capacity density of the catholyte 122 may be about 93.8 Ah/L.
However, the present disclosure is not limited to any particular
permanganate compound concentration.
[0070] Accordingly, embodiments cells and/or stacks (for example
any of the cells 100, 302 and/or stacks 392, 300, 301) may include
a combination of a polysulfide anolyte solution and metal
permanganate catholyte solution. In various embodiments, the metal
permanganate catholyte may be an alkali permanganate catholyte,
such as sodium permanganate (e.g., NaMnO.sub.4), potassium
permanganate and/or lithium permanganate catholyte solution. In
various embodiments, the polysulfide anolyte solution may be a
sodium polysulfide as an active material. In various embodiments,
the anolyte and catholyte may be aqueous alkaline (i.e., pH>7)
solutions.
[0071] For example, with regard to cells that include the
permanganate compounds as a cathode active material, the positive
electrode reaction, which occurs in the catholyte during
discharging, may be written as:
MnO.sub.4.sup.-+e.sup.-.fwdarw.MnO.sub.4.sup.2-, with a half cell
reaction of E.sup.0=+0.60 V vs. standard hydrogen electrode (SHE).
The negative electrode reaction, which occurs in the anolyte 124
during discharging, may be written as:
2S.sub.2.sup.2-.fwdarw.S.sub.4.sup.2+2e.sup.-, with a half cell
reaction of: E.sup.0=-0.45 V vs. SHE, giving a net cell discharge
reaction of
2S.sub.2.sup.2-+2MnO.sub.4.sup.-.fwdarw.2MnO.sub.4.sup.2-+S.sub.4.sup.2-
with a full cell voltage of 1.05 V. In certain embodiments where
Na.sup.+ is used as a working ion of the electrolyte, the net cell
reaction may be expressed as
2Na.sub.2S.sub.2+2NaMnO.sub.4.fwdarw.2Na.sub.2MnO.sub.4+Na.sub.2S.sub.4,
with the charged state materials on the left and the discharged
state materials on the right.
[0072] In various embodiments, permanganate compound active
materials in the aqueous catholyte 122 may be unstable in alkaline
conditions. For example, permanganate compounds may self-discharge
and/or decay to form a solid precipitate. The solid precipitate may
comprise solid manganese oxide (e.g., MnO.sub.2) that is
precipitated from the permanganate catholyte 122. For example,
permanganate cells may self-discharge through the following
reaction:
4MnO.sub.4.sup.-+4OH.sup.-.fwdarw.4MnO.sub.4.sup.2-+2H.sub.2O+O.sub.2.
For example permanganate cells may decay through the following
reaction:
3MnO.sub.4.sup.2-+2H.sub.2O.fwdarw.2MnO.sub.4.sup.-+MnO.sub.2+4OH.sup.-.
[0073] Accordingly, the self-discharge may result in unbalanced
capacity between an AqMn catholyte 122 and an AqS anolyte 124.
According to various embodiments of the present disclosure, this
unbalanced capacity may be addressed by rebalancing the catholyte
122 and anolyte 124 capacities. For example, anolyte capacity may
be reduced by periodically adding oxidation agents to the anolyte
124, such as elemental sulfur (i.e., zero-valent sulfur (SO)). As a
result, the state of charge (SoC) of the anolyte 124 may be reduced
and a consistent ratio of catholyte to anolyte energy density may
be maintained. Excess electrolyte may be drained from the anolyte
124 in order to maintain anolyte volume.
[0074] In some embodiments, the unbalanced capacity may be
addressed by configuring an auxiliary cell in which the negative
electrode is configured to perform the oxygen reduction reaction
(ORR): O.sub.2+H.sub.2O+4e.sup.-.fwdarw.4OH.sup.-, while the AqMn
catholyte is used as the positive electrode. For example, the
anolyte may be a 6M NaOH aqueous solution and anode may be an ORR
electrode such as a carbon support decorated with a manganese oxide
catalyst. In various other embodiments ORR catalyst include any one
or more of iron nickel, platinum, silver, etc., or metal oxide
catalysts, such as manganese oxide (MnO.sub.2), nickel oxide
(NiO.sub.x), nickel oxyhydroxide (NiO.sub.x(OH).sub.y), iron oxide
(FeO.sub.x), iron oxyhydroxide (FeO.sub.x(OH).sub.y), cobalt oxide
(Co.sub.3O.sub.4), etc. In certain embodiments the catalyst may
include or comprise a mixed metal oxide, such as nickel iron oxide
(Ni.sub.zFe.sub.1-zO.sub.x), manganese ferrite (MnFe.sub.2O.sub.4),
zinc ferrite (ZnFe.sub.2O.sub.4), nickel cobaltate
(NiCo.sub.2O.sub.4), lanthanum strontium manganate
(La.sub.0.8Sr.sub.0.2MnO.sub.3), etc. Accordingly, the oxygen
generated due to AqMn self-discharge can be 100% utilized to match
the capacity of both catholyte 122 and anolyte 124. In various
embodiments this auxiliary cell may be in line with the main
reactor or may be a separate cell which may be valved off or
otherwise hydraulically disconnected when not in use. In various
embodiments the catholyte solution may be static or flowing.
[0075] In other embodiments, the manganese oxide precipitate may be
controlled by configuring the separators 316 to remove the
precipitate from the catholyte 122 and/or by including a converter
in the catholyte 122 to dissolve the solid precipitate into the
liquid solution. In other embodiments, small amounts of alkaline
earth metal salts (e.g., BaMnO.sub.4) may be added to the catholyte
122 to form sparingly soluble manganese salts to prevent the
decomposition of active permanganate compounds. In other
embodiments, alkaline earth metal carbonate salts (e.g.,
MgCO.sub.3, CaCO.sub.3, SrCO.sub.3) may be added to the catholyte
122 to reduce the permanganate self-discharge rate. In other
embodiments, alkaline earth metal hydroxide (e.g., Mg(OH).sub.2,
Ca(OH).sub.2, Sr(OH).sub.2) may be added to the catholyte 122 to
reduce the permanganate self-discharge rate. In other embodiments,
a bismuth oxide may be added to the catholyte 122 to reduce the
self-discharge rate.
[0076] Light exposure may also increase the self-discharge rate of
permanganate compounds. Accordingly, in some embodiments, the
catholyte tank 202, tubing 212 and/or components of the stack 300,
301, 392 may be made opaque to prevent the exposure of the
permanganate compounds of catholyte 122 to light.
[0077] In other embodiments, the system 200 may be configured to
increase the oxygen pressure applied to the catholyte 122, in order
to reduce the self-discharge rate of permanganate compounds. For
example, the system 200 may include a pressurized catholyte tank
202 and an optional air pump and/or pressure gauge 230.
[0078] The presence of nickel in the catholyte 122 may also
catalyze the self-discharge and precipitation of permanganate
compounds. Accordingly, the catholyte 122 may be formed using
materials that are substantially free of nickel. In the
alternative, nickel chelating additives may be included in the
catholyte 122, such as ethylenediaminetetraacetic acid (EDTA) or
the like, to sequester nickel. As such, the sequestered nickel may
be prevented from reacting with the permanganate compounds.
[0079] FIG. 4 is a polarization curve for an embodiment flow cell,
and FIG. 5 is a graph showing initial electrochemical cycling data
for the flow cell, when tested at room temperature (about
23.degree. C.). The flow cell included 2.0M NaMnO.sub.4 and 2.8M
NaOH in water (H.sub.2O) as a catholyte, and 2.2M Na.sub.2S.sub.2
and 2.2M NaOH in water as an anolyte. The anolyte and catholyte
were circulated through a flow cell at a flow rate of 0.4
mL/min/cm.sup.2. The flow cell included a graphite felt cathode, a
nickel (Ni) felt anode, and a polytetrafluoroethylene
(PTFE)-reinforced Na.sup.+ ion exchange membrane as a separator.
The flow cell had an observed open circuit voltage (ball-dash line
in FIG. 4) of 1.2V and the measured peak power density (square-dash
line in FIG. 4) was 32.3 mW/cm.sup.2, which may be translated to an
effective area specific resistance (ASR) of 11.8
.OMEGA.-cm.sup.2.
[0080] Referring to FIG. 5, the anolyte and catholyte tank volumes
were each .about.10 milliliters (mL). The cell was cycled under a
constant power condition, with a power density of 14 mW/cm.sup.2.
The cell voltage V is plotted on the left hand axis, while the cell
current C is plotted on the right hand axis. The cell was
discharged for approximately 10 hours, at which time the discharge
was halted and the cell was rested in an open circuit condition for
15 minutes. Following the open circuit rest, the cell was charged
for approximately 8 hours, at which time the test was manually
terminated.
[0081] In various embodiments (for example any of the cells 100,
302 and/or stacks 392, 300, 301), the energy density of the anolyte
and catholyte solutions can be high. For example, with a catholyte
concentration of 3.5M MnO.sub.4.sup.2- and an anolyte concentration
of 2.5M S.sub.2.sup.2-, the total energy density may be 41.0
Watt-hours per liter (Wh/L) for capacity matched solutions,
assuming the full cell voltage of 1.05 V. In various embodiments,
the present disclosure advantageously provides electrochemical
systems having higher energy densities as compared to conventional
aqueous battery chemistries.
[0082] Iron-Cyanide Based Cathode Active Materials
[0083] In some embodiments (for example any of the cells 100, 302
and/or stacks 392, 300, 301), the cathode active material may
include one or more iron-cyanide based compounds. Herein, an
"iron-cyanide based compound" is intended to encompass compounds
including ferrocyanide compounds and ferricyanide compounds. For
example, the cathode active material may include salts comprising
ferrocyanide anions [Fe(CN).sub.6].sup.4- and/or ferricyanide
anions [Fe(CN).sub.6].sup.3-, and cations such as Li, K, and/or Na.
The catholyte 122 may include the ferrocyanide compound dissolved
in an electrolyte, such as an aqueous electrolyte. For example, the
catholyte 122 may have am iron-cyanide compound concentration
ranging from about 0.5 M to about 5 M, such as from about 1 M to
about 3 M, or from about 1.2 M to about 2 M. However, the present
disclosure is not limited to any particular ferrocyanide
concentration.
[0084] It has been found that when mixed monovalent cations are
used in a ferrocyanide catholyte, the potential of the redox pair
was increased. Therefore, in various embodiments, ferrocyanide
catholytes may include mixed cations, such as any combination of
Na.sup.+, K.sup.+, and Li.sup.+ species, rather than a single
cation species.
[0085] Sulfur-Based Cathode Active Materials
[0086] In some embodiments (for example any of the cells 100, 302
and/or stacks 392, 300, 301), the cathode active material may
include one or more sulfur-based compounds. Herein, a "sulfur-based
compound" is intended to encompass sulfur, sulfides, polysulfides,
and transition metal sulfide compounds, and salts thereof. In some
embodiments, the catholyte 122 may include the sulfur-based cathode
active materials dissolved in an electrolyte, such as an aqueous
electrolyte, and may be referred to as an aqueous sulfur (AqS)
compound. For example, cathode active materials may include, sulfur
(S.sub.8), lithium (poly)sulfides (Li.sub.2S.sub.x, where x=1 to
8), sodium (poly)sulfides (Na.sub.2S.sub.x, where x=1 to 8) and/or
potassium (poly)sulfides (K.sub.2S.sub.x, where x=1 to 8). In some
embodiments, the catholyte 122 may include a transition metal
sulfide, such as TiS.sub.x, FeS.sub.x, and/or MnS.sub.x, [wherein
x=1 or 2] may provide a high operating voltage and a corresponding
energy density, and may also be highly resistive to polysulfide
crossover.
[0087] For example, the catholyte 122 may include the sulfur-based
compound at a concentration ranging about 4 M to about 14 M, such
as from about 5 M to about 12 M, or from about 7 M to about 10 M.
However, the present disclosure is not limited to any particular
amount of sulfur compound.
[0088] With regard to cells 100, 302 that may include the
sulfur-based compounds as an anode active material (e.g., dual
sulfur cells), various sulfur species may be formed during charging
and discharging, such that anode and cathode may include different
sulfur species.
[0089] During discharging, the following Reactions 1 and 2 may
occur in the positive electrode
S.sub.8+2e.sup.-.fwdarw.S.sub.8.sup.2- Reaction 1:
2Na.sup.++S.sub.8+2e.sup.-.fwdarw.2Na.sub.2S.sub.8 Reaction 2:
[0090] Other sulfur species may also be generated, such as
Na.sub.2S.sub.5, Na.sub.2S.sub.4, Na.sub.2S.sub.3, etc. During
discharging, the reactions may be reversed. As such, the overall
positive electrode charging and discharging reactions in the
positive electrode may be represented by the following Reaction
3:
S.sub.8+Na.sub.2SNa.sub.2S.sub.x Reaction 3:
[0091] In addition, by changing the ratios of S.sub.8 and
Na.sub.2S, the reaction may be modified, as shown in Reaction 4
below:
S.sub.8+8Na.sub.2S8Na.sub.2S.sub.2 Reaction 4:
[0092] In addition, during discharging, the following Reaction 5
may occur in the negative electrode:
2Na.sub.2S.fwdarw.2Na.sup.++2e.sup.-+Na.sub.2S.sub.2 Reaction
5:
[0093] In some embodiments, a cell may be assembled in a discharged
state, such that the positive and negative electrodes both include
a slurry comprising Na.sub.2S.sub.3. During charging, Reaction 6
may occur in the positive electrode and Reaction 7 may occur in the
negative electrode:
2Na.sub.2S.sub.3.fwdarw.Na.sub.2S.sub.6+2Na++2e.sup.- Reaction
6:
2Na.sub.2S.sub.3+2e.sup.-+2Na+.fwdarw.3Na.sub.2S.sub.2 Reaction
7:
[0094] Many variations on these reaction schemes are possible
according to the invention, including the substitution of lithium
or potassium for sodium, or by tuning the ratio of electropositive
ion to sulfur in each of the cathode and anode electrodes.
[0095] FIG. 6 is a graph showing the various sulfur and polysulfide
species formed during the cycling of an aqueous sulfur electrode
including lithium as an electropositive element. The lower voltage
trace shows the reduction reactions (discharge for the negative
electrode, charge reactions for the positive electrode) proceeding
from a fully oxidized sulfur electrode (S.sub.8). As the electrode
is reduced, Li is added and the electrode moves into a solution
regime, in which soluble polysulfide species such as
Li.sub.2S.sub.8, and Li.sub.2S.sub.4 are formed, and as reduction
continues, it proceeds to Li.sub.2S precipitation. As the direction
of current is reversed (charge for the negative electrode,
discharge for the positive electrode) the reactions are reversed
and the higher voltage trace is followed. As can be seen in FIG. 6,
this initially involves the dissolution of Li.sub.2S in the
electrode moves back into the solution regime; ultimately as the
electrode is further oxidized, elemental sulfur (S.sub.8) is
precipitated back out in the "Sulfur precipitation" regime. These
reactions and mechanisms are known in the art but are recounted
here for clarity.
[0096] Table 1 below is an initial cost analysis of a dual sulfur
stack, according to various embodiments of the present
disclosure.
TABLE-US-00001 TABLE 1 5M [S] 8M [S] 5M [S] Chemistry 0.45 V 0.45 V
0.55 V Chemicals Costs 10.1 8.9 8.3 ($/kWh) Cost of Energy 30.2
22.6 24.7 [Chemicals, Tanks, Efficiency] ($/kWh) Solution Energy
13.4 21.4 16.4 Density (Wh/L) Power Components 368 368 247 Cost
($/kW)
[0097] As can be seen in Table 1, the energy density and area
specific resistance (ASR) may strongly affect the power component
costs per kW.
[0098] In some embodiments, the anolyte 124 may include a
polysulfide compound active material, the catholyte 122 may be an
alkaline solution that does not include an active material (e.g.,
redox pair), and the cathodes 312 may be air electrodes that
comprise a catalyst such as Pt, Ir, Ru, Mn, Ni and alloys thereof.
Accordingly, the cells 100, 302 and/or stacks 392, 300, 301 may use
oxygen from air during discharging, and the tank 202, pump 222, and
tubing 212 may be omitted from the system 200.
[0099] In other embodiments, additional sulfur may be added to the
anolyte 124. Accordingly, the cells 100, 302 and/or stacks 392,
300, 301 may be referred to as "refuel-able"cells/stacks. Since air
is free and sulfur is a low cost material that may be derived from
industrial waste, such a configuration may be used to inexpensively
store power for long periods.
[0100] It is believed that polysulfide in an electrolyte has a
tendency to decay into sodium thiosulfate (Na.sub.2S.sub.2O.sub.3)
and thus, permanently lower the system capacity. Therefore, in
various embodiments (for example any of the cells 100, 302 and/or
stacks 392, 300, 301), relatively small amounts of sodium
thiosulfate may be added to a polysulfide electrolyte, in order to
reduce the decay of polysulfide by altering reaction kinetics. In
other embodiments, elemental sulfur may be added to system
electrolytes, in order to recover capacity and minimize operating
costs.
[0101] According to various embodiments of the present disclosure,
provided are electrochemical cells (e.g., cells 100, 302)
configured to operate using various sulfide, ferrocyanide, and/or
permanganate or manganate chemistries. The cells provide for long
term power storage at unexpectedly low costs per kW. The low costs
per kilowatt hour (kWh) and per kW make various embodiments
well-suited to long-duration and ultra-long-duration energy storage
applications, which require low-capital-cost energy storage
systems.
[0102] In various embodiments, a polysulfide battery may include an
aqueous liquid catholyte contacting a cathode current collector in
a cathode chamber, an aqueous liquid anolyte contacting an anode
current collector in an anode chamber, and a separator separating
the catholyte in the cathode chamber from the anolyte in the anode
chamber. In various embodiments, the anolyte may include an aqueous
alkaline cation polysulfide solution, such as Li.sub.2S.sub.x,
Na.sub.2S.sub.x, and/or K.sub.2S.sub.x solution, in which x ranges
from 1 to 8 (e.g., Li.sub.2S Na.sub.2S and/or K2S when x=1). In
various embodiments, the battery may be a flow battery (i.e.,
flowing battery, which is also sometimes called a regenerative fuel
cell) containing a pump which circulates the catholyte and/or the
anolyte, or a non-flowing battery which lacks the circulation
pump.
[0103] Separators/Membranes
[0104] Various embodiments of the present disclosure include
electrochemical cells (for example any of the cells 100, 302, 700,
800) that include separators and/or membranes that have certain
characteristics. In this disclosure, the terms "membrane" and
"separator" may be used interchangeably. The following discussion
of membranes and separators are provided to illustrate various
aspects of the disclosure and the membranes and separators
discussed below may be applied to any of the embodiment cells
and/or stacks described herein, such as any of cells 100, 302, 700,
800 and/or stacks 392, 300, 301). Membranes of the present
disclosure may, in some embodiments, have a thickness of about 500
microns or less, about 200 microns or less, about 100 microns or
less, about 50 microns or less, or about 25 microns or less.
Suitable separators may be capable of operating in electrochemical
cell with a current efficiency of at least about 80%, at a current
density of 10 mA/cm, when the separator has a thickness of 100
microns or less. More preferably, the electrochemical system is
capable of operating at a current efficiency of at least 90%, when
the separator has a thickness of about 50 microns or less, a
current efficiency of at least 95% when the separator has a
thickness of about 25 microns or less, and a current efficiency of
at least 98% when the separator has a thickness of about 10 microns
or less. Suitable separators include those separators in which the
electrochemical system is capable of operating at a voltage
efficiency of at least 60% with a current density of about 10
mA/cm. More preferably, suitable separators include those
separators in which the electrochemical system is capable of
operating at a voltage efficiency of at least 70%, at least 80% or
at least 90%. Separators are generally categorized as either solid
or porous. Solid membranes can be made from organic materials, such
as polymer, or inorganic materials, such as ceramic and metal
oxide, and typically comprise one or more types of ion-exchangeable
functional groups, wherein the functional groups facilitates mobile
ion transport through the body of the membrane. The facility with
which ions conduct through the membrane can be characterized by a
resistance, typically an area resistance in units of .OMEGA.
cm.sup.2. The area resistance is a function of inherent membrane
conductivity and the membrane thickness. Thin membranes are
desirable to reduce inefficiencies incurred by ion conduction and
therefore can serve to increase voltage efficiency of the energy
storage device. Active material crossover rates are also a function
of membrane thickness, and typically decrease with increasing
membrane thickness. Crossover represents a current efficiency loss
that is generally balanced with the voltage efficiency gains by
utilizing a thin membrane. The active material present in the first
electrolyte and the active material present in the second
electrolyte are separated by the membrane. The diffusion rate of
active materials in either the first electrolyte or the second
electrolyte should be about 1.times.10.sup.-8 mol/(cm.sup.2 sec) or
less, about 1.times.10.sup.-10 mol/(cm.sup.2 sec) or less, about
1.times.10.sup.12 mol/(cm.sup.2 sec) or less, or 1.times.10.sup.-14
mol/(cm.sup.2 sec) or less. Other embodiments of this invention
include situations where the first electrolyte and second
electrolyte are intermixed.
[0105] In some embodiments, the separators may be porous membranes.
Porous membranes are non-conductive membranes which allow working
ions transfer between two electrodes via open channels filled with
electrolyte. This permeability increases the probability of active
materials passing through porous membrane from one electrode to
another causing cross-contamination and/or reduction in cell energy
efficiency. The degree of this cross-contamination depends on,
among other features, the size (the effective diameter and channel
length), and character (hydrophobicity/hydrophilicity) of the
pores, the nature of the electrolyte, and the degree of wetting
between the pores and the electrolyte. The pore size distribution
is generally sufficient to substantially prevent the crossover of
active materials between the two electrolyte solutions.
[0106] Suitable porous membranes may have an average pore size
distribution of between about 0.001 nm and 10 microns. Preferably,
the average pore size distribution should be between about 0.01 nm
and 100 nm. The pore size distribution in a porous membrane can be
substantial. In other words, a porous membrane may contain pores
with a very small diameter (approximately less than 1 nm) and may
contain pores with a very large diameter (approximately greater
than 100 nm). The larger pore sizes can lead to a higher amount of
active material crossover. The ability for a porous membrane to
substantially prevent the crossover of active materials will depend
on the relative difference in size between the average pore size
and the active material. For example, when the active material is
an ionic group in the form of a hydrated complex, the average
diameter of the hydrated complex is about 50% greater than the
average pore size of the porous membrane. On the other hand, if the
porous membrane has substantially uniform pore sizes, it is
preferred that the average diameter of the hydrated complex be
about 20% larger than the average pore size of the porous
membrane.
[0107] According to various embodiments of the present disclosure,
membranes may comprise any suitable polymer, typically an ion
exchange resin, for example, comprising a polymeric anion or cation
exchange membrane, or combination thereof. The mobile phase of such
a membrane may comprise, and/or is responsible for the primary or
preferential transport (during operation of the battery) of at
least one mono-, di-, tri-, or higher valent cation and/or mono-,
di-, tri-, or higher valent anion, other than protons or hydroxide
ions. Suitable solid cationic exchange polymers include use of one
or more of the following polymers: cross-linked halogenated
alkylated compound with a polyamine, a cross-linked aromatic
polysulfone type polymer with a polyamine, perfluoriniated
hydrocarbon sulfonate ionomers, sulfonated polyether ether ketone
(S-PEEK), sulfonated poly(phthalazinone ether ketone), sulfonated
phenolphthalein poly(ether sulfone), sulfonated polyimides,
sulfonated polyphosphazene, sulfonated polybenzimidazole, aromatic
polymers containing a sulfonic acid group, sulfonated
perfluorinated polymer, fluorinated ionomers with sulfonate groups,
carboxylate groups, phosphate groups, boronate acid groups,
polyaromatic ethers with sulfonate or carboxylate groups,
poly(4-vinyl pyridine, poly(2-vinyl pyridine),
poly(styrene-b-2-vinylpyridine), poly(vinyl pyrrolidine),
poly(1-methyl-4-vinylpyridine),
poly(2,2'-m-phenylene)-5,5'-bibenzimidazole
poly(2,2'-(m-phenylene)-5,5'-bibenzimidazole,
poly(2,5-benzimidazole), polyacrylate, polymethacrylate, or
combinations thereof. Suitable solid anionic exchange membranes
include the use of one or more of the following polymers:
polydiaryl dimethyl ammonium, poly(methacryloyloxyethyl
triethylammonium), poly(diallylammonium), or combinations
thereof.
[0108] In some embodiments, substantially non-fluorinated membranes
that are modified with sulfonic acid groups (or cation exchanged
sulfonate groups) may also be used. Such membranes include those
with substantially aromatic backbones, e.g., poly-styrene,
polyphenylene, bi-phenylsulfone, or thermoplastics such as
polyetherketones or polyethersulfones. Membranes may also include
polyesters, poly(ether-ketone-ether-ketone-ketone), poly(vinyl
chloride), vinyl polymers, substituted vinyl polymers, alone or in
combination of any previously described solid or porous polymer
[0109] Membranes according to various embodiments may also comprise
reinforcement materials for greater stability. Reinforcement
materials can be implemented in the membrane as mesh, thin layers,
woven, or dispersion. Suitable reinforcement materials include
nylon, cotton, polyesters, crystalline silica, crystalline titania,
amorphous silica, amorphous titania, rubber, asbestos wood or
combination thereof.
[0110] According to various embodiments of the present disclosure,
separators may include polymer-inorganic composite membranes.
Because such membranes contain no inherent ionic conduction
capability, such membranes are typically impregnated with additives
in order to introduce porous structure. These membranes typically
include a mixture of a polymer and an inorganic filler, and have an
open porosity. Suitable polymers include those chemically
compatible with the electrolytes of the presently described
systems, including high density polyethylene, polypropylene,
polyvinylidene difluoride (PVDF), or polytetrafluoroethylene
(PTFE). Suitable inorganic fillers may include silicon carbide
matrix material, titanium dioxide, silicon dioxide, zinc phosphide,
and cerium dioxide, and may be supported internally with a
substantially non-ionomeric structure, including mesh structures or
the like.
[0111] Suitable membranes also comprise continuous composite
membranes. Continuous composite membranes comprise at least a
material that has a continuous or discontinuous structure and a
filler material that has a continuous or discontinuous structure.
Suitable materials having a continuous or discontinuous structure
may comprise one or more of polyethylene, polypropylene,
poly(tetrafluoroethylene), poly(vinyl chloride), or a combination
thereof. Suitable filler material may comprise nonwoven fibers or
naturally occurring substances. Suitable nonwoven fibers may
include fibers formed of nylon, cotton, polyesters, crystalline
silica, amorphous silica, amorphous titania, crystalline titania,
or a combination thereof. Suitable naturally fibers may be formed
of rubber, asbestos, wood, or combinations thereof. The continuous
composite membranes may also be porous. Suitable porosity may range
from about 1% to about 50% volume fraction.
[0112] Suitable separators may also comprise at least two layers of
the above described membranes. For instance, a suitable separator
comprises a porous layer and a solid layer. For instance, a
suitable separator may comprise a polymeric solid layer and
inorganic solid layer. For instance, a suitable separator may
comprise two layers capable of selective ion transport, such as any
of the above mentioned solid cationic or anionic polymers. Other
layers are included within the scope of this invention that may
enhance or reduce properties such as conduction, strength,
thickness, selectivity, permeability, or the like.
[0113] There may be a significant difference in the concentration
of active material species in the positive and negative
electrolytes in a cell. Despite the presence of the separator, some
finite flux of active materials species across a membrane may occur
due to these concentrations differences, since substantially all
separators exhibit some permeability. When these species crossover
the separator, a loss of energy efficiency occurs, since charged
species are self-discharging through direct interaction. However,
the potential for electrolyte regeneration exists, if a cell
employs different active material compounds.
[0114] Accordingly, suitable separators may be configured to be
effectively impermeable to active materials. Herein, "effectively
impermeable" refers to preventing crossover of at least about 90%
of at least one of the active materials, for a time period of about
year or longer. Preferably, the separators of the present
disclosure are capable of preventing crossover at least about 99.0%
of active materials, such as at least about 99.9% of active
materials, for a period of about a year or more.
[0115] In various embodiments, an anion exchange membrane separator
with small pore size may be used in an aqueous polysulfide battery
containing a polysulfide anolyte active material. The separator
permits transition of a small anion, such as a hydroxide (OHF)
anion, between the catholyte and anolyte chambers. This separator
membrane blocks cations, such as sodium ions, due to its charge
repelling features, and blocks large anions, such as permanganate
anions, due to its small pore size. For example, the separator may
be a porous separator having an average pore size of about 10 nm or
less.
[0116] The separator can be used with a permanganate cathode active
materials or other suitable cathode active materials, such as
sodium or lithium sulfate compounds. Various embodiment anion
exchange membrane differs from the cation exchange membrane
separators that permit transition of alkali cations (e.g., sodium
and/or lithium cations) between the catholyte and the anolyte
chambers.
[0117] For example, various embodiments provide composite membrane
separators that include multiple polymeric membranes that are
physically or chemically bonded together. The polymeric membranes
can be ion exchange membranes, such as anion exchange membranes
(AEM), cation exchange membranes (CEM), etc., or porous membranes
such as nanofiltration membranes, ultrafiltration membranes,
reverse osmosis membranes, polybenzimidazole-based membranes (PBI),
membranes including polymers of intrinsic microporosity (PIM),
etc., or the combinations thereof.
[0118] In some embodiments, a separator may include one membrane
layer including both electrophilic groups, such as anion exchange
groups, and nucleophilic groups, such as cation exchange groups.
For example, a separator may include one or more bipolar membranes.
In some embodiments, a separator may include organic and inorganic
compounds. For example, the separator may be a blended or
multi-layered membrane separator.
[0119] Most commercially available membrane separators, such as
hydrocarbon membranes, are not compatible with permanganate
compound active materials, due to the oxidative nature of aqueous
permanganate compounds (AqMn) with respect to hydrocarbons.
Accordingly, various embodiments provide membrane separators
configured to transfer hydroxide ions, while resisting oxidation by
AqMn compounds.
[0120] For example, various embodiments provide hydrocarbon
membranes coated with a thin layer of an organic or inorganic film
that is resistant to oxidation by AqMn compounds. Coating methods
may include solution casting, co-extrusion, surface cross linking,
and spin coating, for example. Organic film materials may include
polyether ether ketones (PEEK), polysulfones, polystyrenes,
polypropylenes, polyethylenes, or the like. The coated organic
layer should be thin enough to still let working ions pass through
while the manganese species are blocked.
[0121] For example, a PEEK reinforced AEM, such as a Fumasep
FAA-3-PK-130 membrane may be suitable for successfully blocking
AqMn. In particular, while not wishing to be bound to a particular
theory, it is believed that such a membrane may become being
covered in MnO.sub.2 after operating in an ex-situ cell, but is
still able to prevent AqMn crossover. It is predicted that if this
protective coating is not present, the membrane polymer may be
easily oxidized in the AqMn electrolyte.
[0122] Accordingly, in some embodiments, an AEM may be coated with
a thin layer of MnO.sub.2 to protect the membrane from the
oxidative AqMn, while limiting the potential increase in
resistance. For example, the membrane may be coated on at least one
side with MnO.sub.2, to prevent AqMn species from reaching membrane
polymers that are susceptible to oxidation. The MnO.sub.2 may be
permeable to hydroxide ions, while blocking AqMn.
[0123] Methods of MnO.sub.2 deposition may include utilizing
high-temperature permanganate to plate MnO.sub.2 on carbon
electrode materials. For instance, electrodeposition of MnO.sub.2
can be formed from electrolysis of manganese sulfate and sulfuric
acid. For instance, MnO.sub.2 can be formed from reaction of
sacrificing layer of the separator and AqMn.
[0124] In various embodiments, a separator may be included between
the catholyte and anolyte chambers that has a reduced active area
that permits ions (e.g., anions) to travel between the chambers by
embedding ion permeable "window" material (e.g., anion exchange
membrane material) in an ion impermeable separator material.
[0125] FIG. 7A is a schematic view of an electrochemical cell 700
including a separator 716 disposed between a catholyte chamber 722
and an anolyte chamber 724, according to various embodiments of the
present disclosure. FIG. 7B is an enlarged front view of the
separator 716 of FIG. 7A. Referring to FIGS. 7A and 7B, the cell
700 may be a static cell. The separator 716 includes a frame 717
and at least one window 719 disposed within the frame 717. In some
embodiments, the separator 716 may also include a peripheral
support 721 to support the frame 717.
[0126] The frame 717 may be formed of an ion impermeable material.
The window 719 may be formed of a cation permeable material.
Accordingly, the separator 716 has a reduced active area which
permits ions (e.g., anions) to travel between the chambers, due to
including the smaller ion-permeable window 719 within the
impermeable frame 717. In particular, the area of the window 719
may be about one quarter of the total area of the separator 716. As
such, the overall cost of the separator 716 is reduced, as compared
to a conventional separator that does not include a frame 717, due
to the frame 717 reducing the amount of the more expensive
permeable material included in the window 719.
[0127] Accordingly, assuming the cell 700 is operated at the same
current density (mA/cm.sup.2.sub.membrane), the cell 700 can have
4.times. the duration with one quarter the membrane costs (along
with other relevant cell components) as compared to a conventional
static cell with the same total length of the cell. Furthermore, it
is possible to leverage "passive" mass transfer enhancement
mechanism such as Joule heat, gravity, concentration gradient,
etc., in the window cell design thanks to the wider design
space.
[0128] FIG. 8 is a schematic view of an electrochemical cell 800
including a separator 816 disposed between a catholyte chamber 822
and an anolyte chamber 824, according to various embodiments of the
present disclosure. Referring to FIG. 8, the cell 800 may be a
static cell including a catholyte chamber 822, an anode chamber
824, and a separator 816 disposed therebetween.
[0129] The chambers 822, 824 may have various geometries, such that
the area of an interface between the chambers 822, 824 is reduced,
as compared to chambers having an interface that is substantially
the same size as a cross-section thereof. In other words, the
height and/or width of a portion of the chambers 822, 824 may be
reduced, such that the area of the separator 816 may be
correspondingly reduced. The geometries of the chambers 822, 824
may also be modified to accommodate electrolyte viscosity,
conductivity, and/or cost.
[0130] In traditional flow battery systems where a tank filled with
either catholyte or anolyte is connected to a stack of electrically
connected cells, shunt current may occur in an electrolyte conduit
due to electrolyte circulation. Accordingly, the shunt current may
reduce system capacity through auto electrical discharge of
electrolyte components. This disclosure describes a new electrolyte
manifold design that aims to minimize or eliminate the shunt
current issue. As shown in the figure below, each anolyte (yellow)
tank feed cells at the same position but in different stacks. The
cells connected in series in a stack do not "see" the electrolyte
from the same tank.
[0131] FIG. 9 is a schematic view of a flow battery system
configured to reduce shunt currents, according to various
embodiments of the present disclosure. Referring to FIG. 9, the
system includes columns of flow cells 900 that are respectively
connected to an electrolyte tank A-G. Adjacent cells 900 of
different columns may be electrically connected, either in series
or parallel. In other words, the cells 900 may be fluidly connected
by column and electrically connected by row.
[0132] Accordingly, the electrically connected cells 900 of each
row are each provided with electrolyte from a different one of the
tanks A-G. Accordingly, the electrically connected cells 900 of
each row do not "see" the electrolyte from the same tank A-F, which
reduces the possibility of shunt currents. Although not shown,
electrolyte output from each of the columns of cells 900 may be
returned to the respective tanks A-G, or may be returned to one or
more additional tanks.
[0133] FIG. 10 shows a portion of an embodiment battery stack 1000.
The battery stack 1000 may be similar to stacks 392, 300, and/or
301 discussed above. The battery stack 1000 may be a tub or other
type of container supporting the one or more cells (e.g., cells
100, 302) forming the battery stack 1000. In an embodiment, the
battery stack 1000 may include a series of rods 1002 coupled to the
outer surface of the walls 1052 of the battery stack 1000. The
series of rods 1002 may include any number of rods 1002, such as
one rod 1002, two rods 1002, three rods 1002, more than three rods
1002, etc. In various embodiments, the rods 1002 may be constructed
of steel or any other electrically conductive material. In various
embodiments, the rods 1002 may provide high columnar strength, such
that the rods 1002 provide not only electrical connection but also
increased strength needed for stacking the battery stack 1000.
[0134] If the rods 1002 are formed integral with the structure
(e.g., the walls 1052), such as if rotary molded from plastic,
then, electrical leads 1010 may pass through the walls 1052 from
one or more current collectors 1014 (e.g., current collectors 118,
120, 318, 320). The electrical leads 1010 may run the length of the
rod 1002 and connect an upper electrical contact plate 1004 at an
upper end of the rod 1002 to a lower electrical contact plate 1006
at a lower end of the rod 1002. In various embodiments, the upper
electrical contact plate 1004 may be configured to fit within a
lower electrical contact plate 1006 of a rod 1002 of another
battery stack 1000 when the battery stacks 1000 are stacked on top
of one another. For example, upper electrical contact plates 1004
may be convex shapes, such as a cone, etc., sized to fit inside the
concave shaped lower electrical contact plates 1006, such as groove
shaped lower electrical contact plates 1006, etc. The rods 1002 may
be solid or may be hollow, such as a cone. In certain embodiments,
the rods 1002 may be hollow, with the lower concave shape
comprising a curved back lip, creating a ring of contact between
the two nested rods 1002. The rods 1002 may provide electrical
contacts for series and/or parallel connections between battery
stacks 1000. In various embodiments, the weight of an upper battery
stack 1000 disposed above a lower battery stack 1000 may maintain
the connections between the upper electrical contact plates 1004
and the lower electrical contact plates 1006 of the respective
batteries 400.
[0135] FIG. 11A shows one example stacked configuration of multiple
embodiment battery stacks 1000. As shown in FIG. 11A, three battery
stacks 1000 may be stacked on top of one another such that the
lower electrical contact plates 106 of an upper battery stack 1000
contact the upper electrical contact plates 1004 of a lower battery
stack 1000. FIG. 11B shows another example stacked configuration of
multiple embodiment battery stacks 1000. As shown in FIG. 11B, four
battery stacks 1000 may be stacked such that one rod 1002 of each
lower battery stack 1000 contacts a respective rod 1002 of the
upper battery stack 1000. While the battery stacks 1000 shown in
FIGS. 10, 11A, and 11B are shown as having cylindrical walls 1052,
cylindrical housings are merely an example of a housing shape and
other shape housings, such as rectangular shaped housings,
irregular shaped housings, etc., may be substituted for the
cylindrical housings in the various embodiments. For example, the
battery stacks 1000 may each be a series of rectangular trays or
beds stackable on one another.
[0136] Various embodiments may provide devices and/or methods for
use in bulk energy storage systems, such as long duration energy
storage (LODES) systems, short duration energy storage (SDES)
systems, etc. As an example, various embodiments may provide
batteries and/or components of batteries (e.g., any of cells 100,
302, 700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.) for bulk energy storage systems, such as
batteries for LODES systems. Renewable power sources are becoming
more prevalent and cost effective. However, many renewable power
sources face an intermittency problem that is hindering renewable
power source adoption. The impact of the intermittent tendencies of
renewable power sources may be mitigated by pairing renewable power
sources with bulk energy storage systems, such as LODES systems,
SDES systems, etc. To support the adoption of combined power
generation, transmission, and storage systems (e.g., a power plant
having a renewable power generation source paired with a bulk
energy storage system and transmission facilities at any of the
power plant and/or the bulk energy storage system) devices and
methods to support the design and operation of such combined power
generation, transmission, and storage systems, such as the various
embodiment devices and methods described herein, are needed.
[0137] A combined power generation, transmission, and storage
system may be a power plant including one or more power generation
sources (e.g., one or more renewable power generation sources, one
or more non-renewable power generations sources, combinations of
renewable and non-renewable power generation sources, etc.), one or
more transmission facilities, and one or more bulk energy storage
systems. Transmission facilities at any of the power plant and/or
the bulk energy storage systems may be co-optimized with the power
generation and storage system or may impose constraints on the
power generation and storage system design and operation. The
combined power generation, transmission, and storage systems may be
configured to meet various output goals, under various design and
operating constraints.
[0138] FIGS. 12-20 illustrate various example systems in which one
or more aspects of the various embodiments may be used as part of
bulk energy storage systems, such as LODES systems, SDES systems,
etc. For example, various embodiment batteries and/or components
described herein (e.g., any of cells 100, 302, 700, 800, 900,
stacks 300, 301, 392, power modules 390, 391, systems 200, etc.)
may be used as batteries and/or components for bulk energy storage
systems, such as LODES systems, SDES systems, etc. As used herein,
the term "LODES system" may mean a bulk energy storage system
configured to may have a rated duration (energy/power ratio) of 24
hours (h) or greater, such as a duration of 24 h, a duration of 24
h to 50 h, a duration of greater than 50 h, a duration of 24 h to
150 h, a duration of greater than 150 h, a duration of 24 h to 200
h, a duration greater than 200 h, a duration of 24 h to 500 h, a
duration greater than 500 h, etc.
[0139] FIG. 12 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
LODES system 1204 may be electrically connected to a wind farm 1202
and one or more transmission facilities 1206. The wind farm 1202
may be electrically connected to the transmission facilities 1206.
The transmission facilities 1206 may be electrically connected to
the grid 1208. The wind farm 1202 may generate power and the wind
farm 1202 may output generated power to the LODES system 1204
and/or the transmission facilities 1206. The LODES system 1204 may
store power received from the wind farm 1202 and/or the
transmission facilities 1206. The LODES system 1204 may output
stored power to the transmission facilities 1206. The transmission
facilities 1206 may output power received from one or both of the
wind farm 1202 and LODES system 1204 to the grid 1208 and/or may
receive power from the grid 1208 and output that power to the LODES
system 1204. Together the wind farm 1202, the LODES system 1204,
and the transmission facilities 1206 may constitute a power plant
1200 that may be a combined power generation, transmission, and
storage system. The power generated by the wind farm 1202 may be
directly fed to the grid 1208 through the transmission facilities
1206, or may be first stored in the LODES system 1204. In certain
cases the power supplied to the grid 1208 may come entirely from
the wind farm 1202, entirely from the LODES system 1204, or from a
combination of the wind farm 1202 and the LODES system 1204. The
dispatch of power from the combined wind farm 1202 and LODES system
1204 power plant 1200 may be controlled according to a determined
long-range (multi-day or even multi-year) schedule, or may be
controlled according to a day-ahead (24 hour advance notice)
market, or may be controlled according to an hour-ahead market, or
may be controlled in response to real time pricing signals.
[0140] As one example of operation of the power plant 1200, the
LODES system 1204 may be used to reshape and "firm" the power
produced by the wind farm 1202. In one such example, the wind farm
1202 may have a peak generation output (capacity) of 260 megawatts
(MW) and a capacity factor (CF) of 41%. The LODES system 1204 may
have a power rating (capacity) of 106 MW, a rated duration
(energy/power ratio) of 150 hours (h), and an energy rating of
15,900 megawatt hours (MWh). In another such example, the wind farm
1202 may have a peak generation output (capacity) of 300 MW and a
capacity factor (CF) of 41%. The LODES system 1204 may have a power
rating of 106 MW, a rated duration (energy/power ratio) of 200 h
and an energy rating of 21,200 MWh. In another such example, the
wind farm 1202 may have a peak generation output (capacity) of 176
MW and a capacity factor (CF) of 53%. The LODES system 1204 may
have a power rating (capacity) of 88 MW, a rated duration
(energy/power ratio) of 150 h and an energy rating of 13,200 MWh.
In another such example, the wind farm 1202 may have a peak
generation output (capacity) of 277 MW and a capacity factor (CF)
of 41%. The LODES system 1204 may have a power rating (capacity) of
97 MW, a rated duration (energy/power ratio) of 50 h and an energy
rating of 4,850 MWh. In another such example, the wind farm 1202
may have a peak generation output (capacity) of 315 MW and a
capacity factor (CF) of 41%. The LODES system 1204 may have a power
rating (capacity) of 110 MW, a rated duration (energy/power ratio)
of 25 h and an energy rating of 2,750 MWh.
[0141] FIG. 13 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
system of FIG. 13 may be similar to the system of FIG. 12, except a
photovoltaic (PV) farm 1302 may be substituted for the wind farm
1202. The LODES system 1204 may be electrically connected to the PV
farm 1302 and one or more transmission facilities 1206. The PV farm
1302 may be electrically connected to the transmission facilities
1206. The transmission facilities 1206 may be electrically
connected to the grid 1208. The PV farm 1302 may generate power and
the PV farm 1302 may output generated power to the LODES system
1204 and/or the transmission facilities 1206. The LODES system 1204
may store power received from the PV farm 1302 and/or the
transmission facilities 1206. The LODES system 1204 may output
stored power to the transmission facilities 1206. The transmission
facilities 1206 may output power received from one or both of the
PV farm 1302 and LODES system 1204 to the grid 1208 and/or may
receive power from the grid 1208 and output that power to the LODES
system 1204. Together the PV farm 1302, the LODES system 1204, and
the transmission facilities 1206 may constitute a power plant 1300
that may be a combined power generation, transmission, and storage
system. The power generated by the PV farm 1302 may be directly fed
to the grid 1208 through the transmission facilities 1206, or may
be first stored in the LODES system 1204. In certain cases the
power supplied to the grid 1208 may come entirely from the PV farm
1302, entirely from the LODES system 1204, or from a combination of
the PV farm 1302 and the LODES system 1204. The dispatch of power
from the combined PV farm 1302 and LODES system 1204 power plant
1300 may be controlled according to a determined long-range
(multi-day or even multi-year) schedule, or may be controlled
according to a day-ahead (24 hour advance notice) market, or may be
controlled according to an hour-ahead market, or may be controlled
in response to real time pricing signals.
[0142] As one example of operation of the power plant 1300, the
LODES system 1204 may be used to reshape and "firm" the power
produced by the PV farm 1302. In one such example, the PV farm 1302
may have a peak generation output (capacity) of 490 MW and a
capacity factor (CF) of 24%. The LODES system 1204 may have a power
rating (capacity) of 340 MW, a rated duration (energy/power ratio)
of 150 h and an energy rating of 51,000 MWh. In another such
example, the PV farm 1302 may have a peak generation output
(capacity) of 680 MW and a capacity factor (CF) of 24%. The LODES
system 1204 may have a power rating (capacity) of 410 MW, a rated
duration (energy/power ratio) of 200 h, and an energy rating of
82,000 MWh. In another such example, the PV farm 1302 may have a
peak generation output (capacity) of 330 MW and a capacity factor
(CF) of 31%. The LODES system 1204 may have a power rating
(capacity) of 215 MW, a rated duration (energy/power ratio) of 150
h, and an energy rating of 32,250 MWh. In another such example, the
PV farm 1302 may have a peak generation output (capacity) of 510 MW
and a capacity factor (CF) of 24%. The LODES system 1204 may have a
power rating (capacity) of 380 MW, a rated duration (energy/power
ratio) of 50 h, and an energy rating of 19,000 MWh. In another such
example, the PV farm 1302 may have a peak generation output
(capacity) of 630 MW and a capacity factor (CF) of 24%. The LODES
system 1204 may have a power rating (capacity) of 380 MW, a rated
duration (energy/power ratio) of 25 h, and an energy rating of
9,500 MWh.
[0143] FIG. 14 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
system of FIG. 14 may be similar to the systems of FIGS. 12 and 13,
except the wind farm 1202 and the photovoltaic (PV) farm 1302 may
both be power generators working together in the power plant 1400.
Together the PV farm 1302, wind farm 1202, the LODES system 1204,
and the transmission facilities 1206 may constitute the power plant
1400 that may be a combined power generation, transmission, and
storage system. The power generated by the PV farm 1302 and/or the
wind farm 1202 may be directly fed to the grid 1208 through the
transmission facilities 1206, or may be first stored in the LODES
system 1204. In certain cases the power supplied to the grid 1208
may come entirely from the PV farm 1302, entirely from the wind
farm 1202, entirely from the LODES system 1204, or from a
combination of the PV farm 1302, the wind farm 1202, and the LODES
system 1204. The dispatch of power from the combined wind farm
1202, PV farm 1302, and LODES system 1204 power plant 1400 may be
controlled according to a determined long-range (multi-day or even
multi-year) schedule, or may be controlled according to a day-ahead
(24 hour advance notice) market, or may be controlled according to
an hour-ahead market, or may be controlled in response to real time
pricing signals.
[0144] As one example of operation of the power plant 1400, the
LODES system 1204 may be used to reshape and "firm" the power
produced by the wind farm 1202 and the PV farm 1302. In one such
example, the wind farm 1202 may have a peak generation output
(capacity) of 126 MW and a capacity factor (CF) of 41% and the PV
farm 1302 may have a peak generation output (capacity) of 126 MW
and a capacity factor (CF) of 24%. The LODES system 1204 may have a
power rating (capacity) of 63 MW, a rated duration (energy/power
ratio) of 150 h, and an energy rating of 9,450 MWh. In another such
example, the wind farm 1202 may have a peak generation output
(capacity) of 170 MW and a capacity factor (CF) of 41% and the PV
farm 1302 may have a peak generation output (capacity) of 110 MW
and a capacity factor (CF) of 24%. The LODES system 1204 may have a
power rating (capacity) of 57 MW, a rated duration (energy/power
ratio) of 200 h, and an energy rating of 11,400 MWh. In another
such example, the wind farm 1202 may have a peak generation output
(capacity) of 105 MW and a capacity factor (CF) of 51% and the PV
farm 1302 may have a peak generation output (capacity) of 70 MW and
a capacity factor (CF) of 31 The LODES system 1204 may have a power
rating (capacity) of 61 MW, a rated duration (energy/power ratio)
of 150 h, and an energy rating of 9,150 MWh. In another such
example, the wind farm 1202 may have a peak generation output
(capacity) of 135 MW and a capacity factor (CF) of 41% and the PV
farm 1302 may have a peak generation output (capacity) of 90 MW and
a capacity factor (CF) of 24%. The LODES system 1204 may have a
power rating (capacity) of 68 MW, a rated duration (energy/power
ratio) of 50 h, and an energy rating of 3,400 MWh. In another such
example, the wind farm 1202 may have a peak generation output
(capacity) of 144 MW and a capacity factor (CF) of 41% and the PV
farm 1302 may have a peak generation output (capacity) of 96 MW and
a capacity factor (CF) of 24%. The LODES system 1204 may have a
power rating (capacity) of 72 MW, a rated duration (energy/power
ratio) of 25 h, and an energy rating of 1,800 MWh.
[0145] FIG. 15 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
LODES system 1204 may be electrically connected to one or more
transmission facilities 1206. In this manner, the LODES system 1204
may operate in a "stand-alone" manner to arbiter energy around
market prices and/or to avoid transmission constraints. The LODES
system 1204 may be electrically connected to one or more
transmission facilities 1206. The transmission facilities 1206 may
be electrically connected to the grid 1208. The LODES system 1204
may store power received from the transmission facilities 1206. The
LODES system 1204 may output stored power to the transmission
facilities 1206. The transmission facilities 1206 may output power
received from the LODES system 1204 to the grid 1208 and/or may
receive power from the grid 1208 and output that power to the LODES
system 1204.
[0146] Together the LODES system 1204 and the transmission
facilities 1206 may constitute a power plant 1500. As an example,
the power plant 1500 may be situated downstream of a transmission
constraint, close to electrical consumption. In such an example
downstream situated power plant 1500, the LODES system 1204 may
have a duration of 24 h to 500 h and may undergo one or more full
discharges a year to support peak electrical consumptions at times
when the transmission capacity is not sufficient to serve
customers. Additionally, in such an example downstream situated
power plant 1500, the LODES system 1204 may undergo several shallow
discharges (daily or at higher frequency) to arbiter the difference
between nighttime and daytime electricity prices and reduce the
overall cost of electrical service to customer. As a further
example, the power plant 1500 may be situated upstream of a
transmission constraint, close to electrical generation. In such an
example upstream situated power plant 1500, the LODES system 1204
may have a duration of 24 h to 500 h and may undergo one or more
full charges a year to absorb excess generation at times when the
transmission capacity is not sufficient to distribute the
electricity to customers. Additionally, in such an example upstream
situated power plant 1500, the LODES system 1204 may undergo
several shallow charges and discharges (daily or at higher
frequency) to arbiter the difference between nighttime and daytime
electricity prices and maximize the value of the output of the
generation facilities.
[0147] FIG. 16 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
LODES system 1204 may be electrically connected to a commercial and
industrial (C&I) customer 1602, such as a data center, factory,
etc. The LODES system 1204 may be electrically connected to one or
more transmission facilities 1206. The transmission facilities 1206
may be electrically connected to the grid 1208. The transmission
facilities 1206 may receive power from the grid 1208 and output
that power to the LODES system 1204. The LODES system 1204 may
store power received from the transmission facilities 1206. The
LODES system 1204 may output stored power to the C&I customer
1602. In this manner, the LODES system 1204 may operate to reshape
electricity purchased from the grid 1208 to match the consumption
pattern of the C&I customer 1602.
[0148] Together, the LODES system 1204 and transmission facilities
1206 may constitute a power plant 1600. As an example, the power
plant 1600 may be situated close to electrical consumption, i.e.,
close to the C&I customer 1602, such as between the grid 1208
and the C&I customer 1602. In such an example, the LODES system
1204 may have a duration of 24 h to 500 h and may buy electricity
from the markets and thereby charge the LODES system 1204 at times
when the electricity is cheaper. The LODES system 1204 may then
discharge to provide the C&I customer 1602 with electricity at
times when the market price is expensive, therefore offsetting the
market purchases of the C&I customer 1602. As an alternative
configuration, rather than being situated between the grid 1208 and
the C&I customer 1602, the power plant 1600 may be situated
between a renewable source, such as a PV farm, wind farm, etc., and
the transmission facilities 1206 may connect to the renewable
source. In such an alternative example, the LODES system 1204 may
have a duration of 24 h to 500 h, and the LODES system 1204 may
charge at times when renewable output may be available. The LODES
system 1204 may then discharge to provide the C&I customer 1602
with renewable generated electricity so as to cover a portion, or
the entirety, of the C&I customer 1602 electricity needs.
[0149] FIG. 17 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
LODES system 1204 may be electrically connected to a wind farm 1202
and one or more transmission facilities 1206. The wind farm 1202
may be electrically connected to the transmission facilities 1206.
The transmission facilities 1206 may be electrically connected to a
C&I customer 1602. The wind farm 1202 may generate power and
the wind farm 1202 may output generated power to the LODES system
1204 and/or the transmission facilities 1206. The LODES system 1204
may store power received from the wind farm 1202. The LODES system
1204 may output stored power to the transmission facilities 1206.
The transmission facilities 1206 may output power received from one
or both of the wind farm 1202 and LODES system 1204 to the C&I
customer 1602. Together the wind farm 1202, the LODES system 1204,
and the transmission facilities 1206 may constitute a power plant
1700 that may be a combined power generation, transmission, and
storage system. The power generated by the wind farm 1202 may be
directly fed to the C&I customer 1602 through the transmission
facilities 1206, or may be first stored in the LODES system 1204.
In certain cases the power supplied to the C&I customer 1602
may come entirely from the wind farm 1202, entirely from the LODES
system 1204, or from a combination of the wind farm 1202 and the
LODES system 1204.
[0150] The LODES system 1204 may be used to reshape the electricity
generated by the wind farm 1202 to match the consumption pattern of
the C&I customer 1602. In one such example, the LODES system
1204 may have a duration of 24 h to 500 h and may charge when
renewable generation by the wind farm 1202 exceeds the C&I
customer 1602 load. The LODES system 1204 may then discharge when
renewable generation by the wind farm 1202 falls short of C&I
customer 1602 load so as to provide the C&I customer 1602 with
a firm renewable profile that offsets a fraction, or all of, the
C&I customer 1602 electrical consumption.
[0151] FIG. 18 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
LODES system 1204 may be part of a power plant 1800 that is used to
integrate large amounts of renewable generation in microgrids and
harmonize the output of renewable generation by, for example a PV
farm 1302 and wind farm 1202, with existing thermal generation by,
for example a thermal power plant 1802 (e.g., a gas plant, a coal
plant, a diesel generator set, etc., or a combination of thermal
generation methods), while renewable generation and thermal
generation supply the C&I customer 1602 load at high
availability. Microgrids, such as the microgrid constituted by the
power plant 1800 and the thermal power plant 1802, may provide
availability that is 90% or higher. The power generated by the PV
farm 1302 and/or the wind farm 1202 may be directly fed to the
C&I customer 1602, or may be first stored in the LODES system
1204. In certain cases the power supplied to the C&I customer
1602 may come entirely from the PV farm 1302, entirely from the
wind farm 1202, entirely from the LODES system 1204, entirely from
the thermal power plant 1802, or from any combination of the PV
farm 1302, the wind farm 1202, the LODES system 1204, and/or the
thermal power plant 1802. As examples, the LODES system 1204 of the
power plant 1800 may have a duration of 24 h to 500 h. As a
specific example, the C&I customer 1602 load may have a peak of
100 MW, the LODES system 1204 may have a power rating of 14 MW and
duration of 150 h, natural gas may cost $6/million British thermal
units (MMBTU), and the renewable penetration may be 58%. As another
specific example, the C&I customer 1602 load may have a peak of
100 MW, the LODES system 1204 may have a power rating of 25 MW and
duration of 150 h, natural gas may cost $8/MMBTU, and the renewable
penetration may be 65%.
[0152] FIG. 19 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
LODES system 1204 may be used to augment a nuclear plant 1902 (or
other inflexible generation facility, such as a thermal, a biomass,
etc., and/or any other type plant having a ramp-rate lower than 50%
of rated power in one hour and a high capacity factor of 80% or
higher) to add flexibility to the combined output of the power
plant 1900 constituted by the combined LODES system 1204 and
nuclear plant 1902.
[0153] The nuclear plant 1902 may operate at high capacity factor
and at the highest efficiency point, while the LODES system 1204
may charge and discharge to effectively reshape the output of the
nuclear plant 1902 to match a customer electrical consumption
and/or a market price of electricity. As examples, the LODES system
1204 of the power plant 1900 may have a duration of 24 h to 500 h.
In one specific example, the nuclear plant 1902 may have 1,000 MW
of rated output and the nuclear plant 1902 may be forced into
prolonged periods of minimum stable generation or even shutdowns
because of depressed market pricing of electricity. The LODES
system 1204 may avoid facility shutdowns and charge at times of
depressed market pricing; and the LODES system 1204 may
subsequently discharge and boost total output generation at times
of inflated market pricing.
[0154] FIG. 20 illustrates an example system in which one or more
aspects of the various embodiments may be used as part of bulk
energy storage system. As a specific example, the bulk energy
storage system incorporating one or more aspects of the various
embodiments may be a LODES system 1204. As an example, the LODES
system 1204 may include any of the various embodiment batteries
and/or components described herein (e.g., any of cells 100, 302,
700, 800, 900, stacks 300, 301, 392, power modules 390, 391,
systems 200, etc.), singularly or in various combinations. The
LODES system 1204 may operate in tandem with a SDES system 2002.
Together the LODES system 1204 and SDES system 2002 may constitute
a power plant 2000. As an example, the LODES system 1204 and SDES
system 2002 may be co-optimized whereby the LODES system 1204 may
provide various services, including long-duration back-up and/or
bridging through multi-day fluctuations (e.g., multi-day
fluctuations in market pricing, renewable generation, electrical
consumption, etc.), and the SDES system 2002 may provide various
services, including fast ancillary services (e.g. voltage control,
frequency regulation, etc.) and/or bridging through intra-day
fluctuations (e.g., intra-day fluctuations in market pricing,
renewable generation, electrical consumption, etc.). The SDES
system 2002 may have durations of less than 10 hours and round-trip
efficiencies of greater than 80%. The LODES system 1204 may have
durations of 24 h to 500 h and round-trip efficiencies of greater
than 40%. In one such example, the LODES system 1204 may have a
duration of 150 hours and support customer electrical consumption
for up to a week of renewable under-generation. The LODES system
1204 may also support customer electrical consumption during
intra-day under-generation events, augmenting the capabilities of
the SDES system 2002. Further, the SDES system 2002 may supply
customers during intra-day under-generation events and provide
power conditioning and quality services such as voltage control and
frequency regulation.
[0155] Various embodiments may provide electrochemical cells
including a cathode including sulfur, an anode including a sulfide,
and an ion-permeable separator configured to electrically insulate
the anode and the cathode from one another. Various embodiments may
include operating the electrochemical cell in a discharge or
charging mode. In various embodiments, a power module may include
one or more stacks including two or more such embodiment
electrochemical cells. Various embodiments may include operating
the power module in a discharge or charging mode.
[0156] Various embodiments may provide electrochemical cells
including a housing having a first chamber and a second chamber, a
catholyte disposed in the first chamber and including a dissolved
ferrocyanide or ferricyanide compound, a cathode immersed in the
catholyte, an anolyte disposed in the second chamber and including
a polysulfide compound, and an ion-permeable separator disposed
between the anolyte and the catholyte and configured to
electrically insulate the anode and the cathode from one another.
In various embodiments the anolyte and the catholyte may include
Li, Na, K, or a combination thereof. In various embodiments, the
cathode may include a carbon felt. In various embodiments, the
cathode may include a nickel foam. In various embodiments, the
electrochemical cell may include a first volume of the catholyte
and a second volume of the anolyte, the first volume being about
three times greater than the second volume. In various embodiments,
an electrochemical stack may include a plurality of such embodiment
electrochemical cells. In various embodiments, a power module may
include one or more such embodiment electrochemical stacks. Various
embodiments may include operating such embodiment electrochemical
cells in a discharge or charging mode.
[0157] Various embodiments may provide electrochemical cells
including a catholyte including a dissolved permanganate or
manganate compound, an anolyte including a polysulfide compound,
and an ion-permeable separator disposed between the anolyte and the
catholyte and configured to electrically insulate the anolyte from
the catholyte. In various embodiments, the catholyte may include an
alkali permanganate catholyte. In various embodiments, the anolyte
may include a sodium polysulfide solution. In various embodiments,
the anolyte and catholyte may be aqueous alkaline solutions. In
various embodiments, the separator may include an anion exchange
membrane which blocks cations and has a pore size that is
sufficiently small to block permanganate anions and that is
sufficiently large to permit transition of hydroxide anions. In
various embodiments, the separator may be disposed within an ion
impermeable separator material disposed between the anolyte and the
catholyte.
[0158] The foregoing method descriptions are provided merely as
illustrative examples and are not intended to require or imply that
the steps of the various embodiments must be performed in the order
presented. As will be appreciated by one of skill in the art the
order of steps in the foregoing embodiments may be performed in any
order. Words such as "thereafter," "then," "next," etc. are not
necessarily intended to limit the order of the steps; these words
may be used to guide the reader through the description of the
methods. Further, any reference to claim elements in the singular,
for example, using the articles "a," "an" or "the" is not to be
construed as limiting the element to the singular. Further, any
step of any embodiment described herein can be used in any other
embodiment.
[0159] The preceding description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
described embodiment. Various modifications to these embodiments
will be readily apparent to those skilled in the art, and the
generic principles defined herein may be applied to other
embodiments without departing from the scope of the disclosure.
Thus, the present invention is not intended to be limited to the
embodiments shown herein but is to be accorded the widest scope
consistent with the following claims and the principles and novel
features disclosed herein.
* * * * *